My advice would be to just do your best and let your teacher correct any mistakes you make. That way she/he will be better able to assess your level and know what kind of help to give you, and you can ask your teacher to explain it to you after you receive your grade.
Yes, that is what I’d suggest as well. Nothing is off-the-wall wrong here so that’s good.
The only thing I’d suggest (and it’s possible your teacher wants them like these so in that case, ignore me), is that much like in English, you don’t need to repeat “my house” each time.
I agree with the other posters - you’re on the right track and your teacher will be able to help correct mistakes for you!
A quick tip though - where you position も in the sentence makes a big difference. When you say うしろ に にわ も あります you’re saying “there’s a garden in the back, along with some other things” - the も here implies that “a garden” is just one of the things you have out back. If you say うしろ に も にわ が あります, on the other hand, it means “there is also a garden behind the house”.
However, if you haven’t covered stacking particles like this (に and も together) in your classes, it’s probably better to stick to the grammar you’ve been taught for your assignment. (You could also just say うしろ も にわ が あります, which is simpler grammar but sounds a little less natural imo.)
However after thinking about this, I do want to say that things that make sentences in English sound “childlike” are fine in Japanese. So don’t let what I said above make it sound like you only need to say long convoluted sentences.
