I finally finished all exams ofin my course inat the uni yesterday, and now that I am a freaking(?) man!

"freaking" is unclear.

However, now I am completely lost as to what I should do.

The original sentence is sensible, but it feels very unnatural and "what I should do" being the object of "lost" feels unclear.

I think you could actually just say "but now I'm completely lost. What should I do with my time?"

In these two weeks, I was pushed to study for the exam, and I was longing to be free!

"exam" is referring to a specific test so it needs "the".

Now I have a plentiful amounty of time, but sarcastironically, I can't see what shall I do,I should do, being suddenly released from hard work.

"plentiful amount of time" is a little unusual because "plentiful" is not a common word, but "plenty of time" is just the more common phrasing.

I feel "being" can make the last clause work because you're describing the state or situation in which you "can't see what [you] shoul d do".

What is the best way for me to rejoiceenjoy my holiday?

Again, "rejoice" is not a common word.

I lost thingsdon't know what to do

I finally finished all exams of my course in the uni yesterday, and now that I am a freakinge man!

"Freaking man" would have a slang connotation of surprise or excitement at suddenly being a man

However, now I completely lostdon't know what I should do.

In these two weeks, I was pushed to study for my exams, and I was longing to be free!

Now I have a plentiful amounty of time, but, sarcasticaltrangely, I can't see what shall I do,figure out what to do now that I am suddenly released from all of the hard work.

What is the best way for me to rejoice my holidaycelebrate?