while this is a pretty lengthy set of exercises, i think practice will make it easier for you. like the directions say, you have to use the bolded word they give you, but you can add more words to help it make more sense, for example:
25) I can't talk for long as my parents think I'm doing my homework.
SUPPOSED
I can't talk for long as I....................my homework.
so, you could make the sentence say "i can't talk for long as i am supposed to be doing my homework." "am supposed to be doing" is 5 words, so that fits the criteria for the problem, and it means something similar--your parents think you're doing you're homework, you're SUPPOSED to be doing your homework.
27) for this one, you could say "the path down the mountain was so slippery that it caused difficulty for us on our feet." -- it was hard for us to stay on our feet, it caused difficulties, same thing. this exercise is sort of weird, forcing you to fit words into a blank that don't yet fit.
if you have any specific ones that trip you up, you can message me and i'll try to help you out more.