You can improvise all you want - with your own sentences and thoughts.
When it comes to expressions and idioms, you learn them and use them exactly as they are; there is no room for improvement, grammar corrections, free styling or synonyms.
You can't say things like "Nobody is happy in the house if the mom is not happy"; nope, not an option.
It's raining cats and dogs - never "dogs and cats", and most definitely, never any other animals.
There are different degrees of idiomaticity: some expressions have meanings that are easy to guess (example: "to bite more than you can chew") and others have to be learned because at first they appear to be a total mystery (example: "to fall off the wagon" or "to put your money where your mouth is"). Obviously, in the first case the meaning is that someone has taken more responsibilities or work than they can handle, or gotten into a situation which is more demanding than they thought it would be. Anyone can figure it out without much effort. However, if you fall off the wagon, you fail at something you decided to change or pursue, like a diet or a fight with an addiction. You were sober but relapsed into drinking? Yep, you fell off the wagon. You hopped on the wagon with good people and support and really good intentions - but lost your nerve or something happened and now you're back into the problem, off the wagon. The idiom about the money and the mouth is my favorite because I totally misunderstood it the first time I run across it and thought it was supposed to mean that money doesn't buy happiness and you can stick it wherever. In reality, however, you put your money where your mouth is when you keep your promise! Crazy, I know!
Once you get into the territory of idioms, you have reached an intermediate level of learning a language - English, French, Spanish or any other. You vocabulary is rich enough and you are able to use it comfortably in a more eloquent way. The trick here is to remember and use the idioms mot-à-mot, as the French say, word-for-word. No improv allowed. If you say that you dropped off the wagon... you said nothing. If you announce that you have more in your mouth than you are able to chew, it doesn't cut it. Sometimes it's funny, but most of the time it's just plain awkward. Don't. No, seriously, don't. You were doing so well showing off all your knowledge; don't ruin everything by declaring you have put your "blood, tears and sweat" into that project - it's "blood, sweat and tears" in that exact order. If you need a drink, you can't say that in some time zone it's probably 5 pm and socially acceptable; "it's 5 o'clock somewhere", no variations. Well, except in French, where cultural differences manifest themselves in a very amusing way, by correcting the acceptable time for a drink to noon: "midi" is a good time to have a glass of wine with lunch in more liberal cultures.
Idioms are fun. Research their origins, find cartoons with their meanings, write a few sentences using them in your own way... They are the salt of the earth, the Holy Grail of language learning, the cherry on top... you get the idea!
Here is my argument in favor of learning a new language: every person around the world has done it! At some point, in some way, from conversations with parents and friends, following songs or TV shows, children form their vocabulary and start learning their mother tongue – naturally, gradually, step by step, year after year.
Nobody was born speaking a language.
So much for the tired excuse: “I’m not good with languages”! Recently, scientists have discovered that children are not really learning more easily or more quickly than us, adults. They spend several hours a day, immersed in the new language at school or out in the street, in a new country, working hard on their new skills, making mistakes, trying again, repeating and slowly going forward. Adults are more self-conscious and more critical; they get discouraged by every mistake, often have unrealistic expectations and, almost all the time, they’re very hard on themselves. Well, we, your teachers, have news for you: learning a language is a process. Make your mistakes – then the teacher will explain and correct you – then you’ll start catching yourself and correcting yourself – and fluency will come with time, practice and dedication.
It's a proven psychological fact that we retain much more when we are interested in the subject of learning. Our memory is very selective this way. Events and experiences that have impressed us or moved us deeply are engraved in our memory, many years later, while we all have boring exams we have passed and completely forgotten about within weeks. Take a sports fan who knows every detail about his favorite team or player, plus stats and scoring situations, championships, positions on the field, etc. I could never remember that, since watching sports is not my cup of tea; but ask me about my favorite musicians, and I will tell you every album, every landmark in their lives - believe it or not, I know every word of every song of my favorite band from the time I was growing up (it's too embarrassing to mention but I still like them), and I have won a bunch of contests and prizes because of my useless trivia knowledge, based on pure interest in the subject.
There is a huge, dangerous misconception about games, music and all visual media as sources of entertainment and nothing more. On top of that, young language learners are presumed distracted and unwilling to learn. Connect the dots, and you have the picture: if your students are lacking in interest or motivation, the reason is most likely boredom. The traditional textbook-workbook-pen-chalk-blackboard concept may be still good, but it most definitely is only a small part of the arsenal a language teacher can use in an attempt to make it a success.
So accept that new language as a new adventure.
Take a deep breath. Jump! The water is great.
One of my students came to class excited today.
He told me how he'd scored 100% on his English grammar test!
Well, that made my day. (That, and the red wine and the good company at our little office party later on.)
But seriously. He stopped using me as a dictionary a few months ago. Shortly after that, he stopped trying to switch back to French when he felt it was too difficult to express himself in English.
I am very, very proud of his progress. He has been working hard, taking 3-4 hours per month on average - which is not a big time or money commitment. But he's persisted. He comes to class with a smile on his face and an open mind, sometimes bringing a school project to fine-tune, and (most of the time) with his homework done.
And that's how learning a second language works.
EVEN FOR A TEENAGER :-)))
A Europe-born-and-raised, but also suburban mother of two, with a passion for languages, cultures, writing, travel and knowledge - combining my 20-something years of teaching and marketing into a language school in the suburbs of Montreal. Quebec, Canada.