I'm pleased to see you've made a real effort with your homework before posting here; generally JF isn't a place for homework help, partly because it is often very clear if you've been helped by a native speaker, and you might be discredited for plagarism! Don't forget- making small mistakes and getting ~proper~ teacher feedback is all part of the learning process; so far you look like you're doing just fine.
Regarding へand に：I've come across the difference being simply explained as 'へ is used when the destination is an event' before. I'm not sure where this idea comes from because it's not really correct.
One reason why へ might be used over にis for the sake of variation:
げつようびにおおさかにいきます has two に, which is fine, but some people may prefer to say げつようびにおおさかへいきます instead-へcan replace the second に but never the 'time' に of course.
but basically
へ indicates a direction or goal, or a destination toward which one is moving or at which one has arrived "to"
so in とうきょう
にいきます the meaning is more like simply "I go to Tokyo"
but in とうきょう
へいきます is more (roughly) like "I head for Tokyo" even though most people would also translate it as "I go to Tokyo" too.
Secondly: I'm sure if you're following a text book they implicitly encourage it, but every one of your translations uses 'わたしは’ or some variant. It's more natural (and more practical!) to just drop it. The grammar implies that you are the subject already, so there's no need to state it unless you really want to.
Regarding number 7 (meeting a friend), I think you've gotten quite muddled in how this sentence should be constructed. You're probably already paying for one teacher, so I'll let them do their job and correct it for you. However, if you still don't understand, or want to practice it, feel free to come back and ask again, ok? We'll be happy to help.