I went to a party today. My friend was throwing a party to celebrate getting through a University. I saw so many things at the party including a lot of potheads chugging beer as there was no tomorrow. I just stood still the whole night.

I'm a native speaker, not a teacher. I agree with the teachers below but here is how I would write it: Today I went to a party to celebrate my friend's graduation from university. (or college, we intermix the two in the US). At the party I saw many things, for example, I saw potheads chugging beer like there was no tomorrow. I just stood still the whole night.

I agree with the previous answer, but would like to add a few corrections. Normally they say “graduate from a University”. And since this action precedes “he wanted to celebrate”, I’d use the Past Perfect tense here: “because my friend had graduated from a University”. Besides, I’d use Past Continuous in the last sentence: “I was just standing still the whole night” (because the period of time is indicated here)

Nice! Funny story in good English. My takeaways for you are as follows: Regarding verb tenses – generally speaking, we use the perfect tense only when no time context is provided, or if the time context is vague and undetermined. That is, "today I was at a party", and "I saw a lot of potheads" (it is clear that you saw them at the time of the party, given the context). Another thing is that a party does not exist the same way a person exists. It's more "spiritual" (there should be a more linguistically accurate term for this). So while the sentence "the main reason for its existence [is] (and not 'because')" isn't grammatically incorrect, it would be better to say "it was being thrown to celebrate ...." or "my friend wanted to celebrate .... so he invited ... " and you can get creative with that. Lastly, two minor fixes are the idiom, which is correctly said "as if there is no tomorrow", and the last sentence, which would be better said "regarding/as for myself". Keep it up :)