Previously, I didn't understand why people posted video contents about studying themselves. Previously, I didn't understand why people posted video contents about studying.

Or: Previously, I didn't understand why people posted video contents about themselves studying.

I also didn't know why other people watched theat contents. I also didn't know why other people watched that content.

Today, I feelt down while doing my study routines. Today, I felt down while doing my study routines.

All the actions in this text are already done. Therefore, use past tense for the whole text.

Today, I feelt down while doing my study routines. Today, I felt down while doing my study routines.

It seems like burn-out orand a lot of stress. It seems like burn-out and a lot of stress.

By accident, I seeaw the study vlog and it hit me that I am participating andI was shocked that I was studying with them. By accident, I saw the vlog and I was shocked that I was studying with them.

I didn't quite understood the phrase 'hit me that I am participating and studying with them', so I presumed that you were surprised or shocked that you are doing the same thing as them.

By accident, I see theaw a study vlog, and it hit me that I am participating and studying with them. By accident, I saw a study vlog, and it hit me that I am participating and studying with them.

The video makes me cheep up andcheered me up to study again. The video cheered me up to study again.

The video makesde me cheepr up and study again. The video made me cheer up and study again.

I finally understanood the people who makde these study vlogs and why they watched them. I finally understood the people who made these study vlogs and why they watched them.

I finally understand the people who make the study vlogs and watch them. I finally understand the people who make study vlogs and watch them.