I'm sorry, I don't know a word of Hebrew, and I really want to know what these sentences mean:
Bar'chu et Adonai ham'vorach l'olam vaed
Baruch atah Adonai
If I didn't write them correctly, please correct me too.
I think you are mixing up 3 different phrases.
Here "barchu" is imperative.
Here, "baruch" is beinoni pa'ul - a type of verb that is so passive and descriptive it may be the closest thing in Hebrew to an adjective without actually being an adjective.
Barchu is a plural imperative verb meaning "bless" (so, because of the plural, you can read that as "y'all bless"). Baruch is a passive participle conveying state; "baruch (noun)" means "blessed is (noun)", or in the case of "baruch atah...", "blessed are you".