I agree with the two other answers: practice, re-read, and edit. You are doing great!
Also, the difference with these two sentences:
1. I am going to take my driving test next week.
You are stating a fact about something that will happen in the future (next week). You are confirming. You are making a statement.
2. I would like to take my driving test.
You are making a statement about your INTENTION. This is something that you want to do, if it's possible.
And yes, saying "I would like" rather than "I want" can be considered more polite. But depending on the context and tone of your voice, "I want" will not be considered rude or impolite.