The youtuber was talking about how to get better mentally.

People who are mentally tiredill tend to use negative expressions.

Or uUsing negative expressions frequently may cause mentally trouble to them.

Heis suggested usions were based on some studies.research.

RememberHe suggested taking five negative words that you use often use, and saytry to express them in othera more positive words.ay.

ASince any word has bothcould have a positive and a negative aspects, try to...

F.... focus on thinking ofe positive words.

It sounds common, but I thHis suggestion sounds easy/logical/obvious, and followinkg it' is a good way to be healthy.

The youtuber was talking about how to get better mentally.

OrFrequently using negative expressions frequently may cause mentally trouble to them issues.

He suggested uthis based on some studies.

Remember five negative words that you use often use, and say them in other more positive wordsversion.

hHow to get better

Titles in English should start with a capital letter.

I watched a Youtube video yesterday.

I would personally put "Yesterday" at the beginning of the sentence, but the way you did it is fine too.

The youtuber was talking about how to get better mentallyimprove one's mental health.

The word "about" is necessary here if you want to use the verb "talking". However, you can replace "talking about" with "discussing" which is what I would do, but either way is correct.

People who are mentally tired tend to use negative expressions.

It's grammatically correct, but I'm not sure what "mentally tired" here is supposed to express. It sounds like the point is to express a negative state of mind (pessimism) from the other sentences, but "mentally tired" in English sounds like you're saying someone who is tired after a long period of mental activity like thinking.

Or using negative expressions frequently may cause mentally trouble to them.

You should not start sentences in English with conjunctions like "or". However, you could write something like this: "That, or using negative expressions frequently may cause mental trouble to them".

He suggested us based on some studies.

If you write "He suggested us", you need to follow it up with a noun describing what he suggested. e.g. He suggested us a bit of advice based on some studies

Remember five negative words that you use often use, and sayreplace them inwith other positive words.

It sounds commonsimple, but I think it's a good way to bestay healthy.

"Common" is just a word that indicates the frequency of something usually without any relation to its quality. The word I would use here is "simple", or "plain". Also "be healthy" sounds more natural in English.

The youtuber was talking about how to get better mentally.

Or using negative expressions frequently may cause mentally t prouble toms for them.

You can also combine this sentence with the one before it to say: "People who are mentally tired tend to use negative expressions, or using negative expressions frequently may cause mental problems for them".

Remember five negative words that you use often use, and say them in other positive words.

Your original sentence is grammatically correct, but saying "you use often" sounds more natural.