Correção de frases "He demonstrated their opinion"

Hi, folks! I've been studying English and I'm learning word and making phrases. I think that it's the place to post it to correct to me. (Qualquer erro (creio há muitos) me avisem para eu ir corrigindo!)

He demonstrated their opinion.
He has covered your demonstration the canvas.
The cover of the house has selected to the film.
Use the paintbrush to fill the shapes.
In any way, shape or form, we'll do it.
Scroll down the page.
The canvas is out of shape.
Your grade are not here. Check out they in my office.
He document is wrong. Redo it.
Fill in the blanks.
The computer is in the default setting.
You have a nice middle.
I'm in the middle of doing my work.
I'm in the middle of nowhere.
I've also been studying math.
Document it to me.