If I was'm at home on the weekends, I would go to wandering around near my house, or do some oil paint to make my minding in order to refreshed.

The original sentence was in past tense which implies these are no longer things that you do. So I changed it to be in the present tense. Note that this type of past tense construction can be used as a hypothetical for the future, but this implies that it's not something you are likely able to do.
Eg: "If I was home this weekend, I would watch that TV show that everyone's excited for." -> this implies that you will most likely *not* be home at the weekend but wish that you could be. On the other hand a sentence like: "If I'm home this weekend, I'll watch that TV show everyone's excited for." implies that you may or may not be home, but in this case that you are you will watch the TV show.

Unfortunately, I only have a fewer friends, so I have to makecheer myself cheer up.

Here "fewer" would only make sense if you're comparing to something else that has been specified. Eg: "I have fewer friends than other people" or "I have fewer friends than I used to". Instead, if you're not comparing, then you should use "a few"

I think this means becomingis what it means to be an adult.

If I was at home on the weekends, I would go to wandering around near my house, or do oil painting to make my mind refresherefresh my mind.

"make my mind refreshed" is grammatically okay, but usually we would say "to refresh my mind"

Unfortunately, I have very fewer friends, so I have to makecheer myself cheer up.

"fewer" is comparative, so it has to compare to something.

I think this is what it means to becominge an adult.