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.
1 ברוך אתה ה Baruch Attah Adonai. This phrase is commonly translated as "Blessed are you Lord," meaning "you, the Lord, are blessed" a statement of fact. It is used to begin most ritual blessings.
2 ברכו את ה המבורך Barechu et Adonai HaMevorach. This phrase means "Bless the Lord-who-is-Blessed." "Bless" here is the plural imperative. This phrase is used by the leader of a public prayer service to call the community to prayer. The proper response by the congragation is:
3 ברוך ה המבורך לעולם ועד Baruch Adonai HaMevorach LeOlam VaEd. This means "Blessed is the Lord-who-is-Blessed forever and ever." This response involves the congregation replying to the leader that, in fact, God is blessed forever and ever.
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".
Bless God, the blessed [one]
Here "barchu" is imperative.
You are blessed, God.
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.