My day began with an uncertainty ofabout when to go to the university, as my lab senior wasn't available.

I had anyway planned to go anyway to the department at about 11:30 am.

"anyway" should be after a verb, not before it.

So, I prepared my dish and was set to go to the university at around 11.:00 am.

We're talking about a specific, unique university, so "the" will be used.

We ate it and enjoyed ourselves a lot.

"Enjoy" feels a little odd without something to BE enjoyed. When used simply to mean "to have fun", we often might use a "-self" pronoun.
Alternatively: "We ate it and had a lot of fun." or "We ate and enjoyed it a lot."

All of us did very well ion the exam.

In this final year of vauniversity, I gothad so many thoughts about life, mostly stressful thoughts.

Looking up the word "varsity", I see it has more to do with the sports of a college or university, rather than just academics.

As I a'm getting older, I have to face more complexity, which makes me a bit sad as I miss the innocent and carefree version of me.

I've contracted "I am" to "I'm" just to make it sound a little more natural, but otherwise you're all good!

My day began with an uncertainty ofabout when to go to the university, as my lab senior lab wasn't available.

I'm not quite sure what you mean by lab senior, but I think you meant senior lab?

I had anywayn any case, I had planned to go to the department at about 11:30 am.

We ate and enjoyed the party a lot.

Meanwhile, during the classes, I got to knowfound out about my classmates' results, as it wasthey were published just the day before yesterday.

All of us did very well ion the exam.

In this final year of varsity, I gothave so many thoughts about life, mostly stressful thoughts.

My day began with an uncertainty ofabout when to go to the university, as my lab senior wasn't available.

I had anyway planned to go to the department anyway at about 11:30 am.

We ate and enjoyed it a lot.

enjoyed usually needs a noun after it to describe what you enjoyed. In this case you can just use "it" if you're talking about the eating that you started in the sentence with.

Meanwhile, during the classes, I got to know about my classmates' results, as it wasthey were published just the day before yesterday.

There's more than one result, so it's "they were" instead of "it was"

In this final year of varsity, I gothave so many thoughts about life, mostly stressful thoughts.