If I open a Crunchyroll account with a friend, can he use the account and can we also watch quwasi at the same time as with netflix?
Yes, you can watch several at the same time at Chrunchyroll (self-tested).
At least two are possible. In addition, I have not yet tested myself.
Then how can I share that?
You create an account and tell your buddy the access data. In exchange, your buddy should regularly pay you half the cost.