Maybe he is lying and flirting with you.

3. You can find a nice partner in your life circle, not only ion the internet.

Just pursue your true love if you really think he is thate one.

We have met before, but 30 years ago.

I think I can，, but I know it is a short and fleeting love because the love is shallow if you don’t suffer troubles and obstacles with him.

Maybe you will feel bad and take exception to my opinion.

formally: You will
informal: you'll
Here, 'you will' matches the context.

We have met before butonly 30 years ago.

Maybe you will feel bad and tmake an exception to my opinion.

Although I know a person who falls in love won’t care about another’s words, at least let me give you some kind suggestions and explanations:

You won’t have a lot of time to stay in love with him in love imagination because you have a lot of stuff to do, like protect your family, support your parents, etc.

Although I want to follow thbe politically correctness, we should take responsibility in this age.

You should find a balance between reality and dreamimagination.

2. You can-not make sure the man is good or bad.

I have seen many playboys hurt girls and never feel guilty, you can not believe a man you only see once.

3. You canshould find a nice partner in your life circlreal life, not only in the internet.

"in real life" is more natural than "in your life circle"

You will have more ways to know a man if he is in your life circlyou know him in real life.

Then it will decrease the probability that you will have beenbe cheatinged on.

We haved met before but 30 years ago.

Sounds more natural

I have seen many playboys hurt girls and never feel guilty, you can not believe a man youwhom you've seen only see once.

Maybe he is lying and flirting with you.

You flirt *with* someone

3. You can find a nice partner in your life circle, not only ion the internet.

The above are my suggestions and it is from a subjective perspective and is kind of one-sided.

Just pursue your true love if you really think he is thate one.

We usually say "the one" in romantic references

We have met before but 30 years ago.

This sentence is correct, but I don't understand what it means in context. Do you mean to say you met someone over the internet 30 years ago and fell in love with them?

I think I can， but I know it is a short and fleeting love because the love is shallow if you don’t suffer troubles and obstacles with him.

Although I know a person who falls in love won’t care about other’s words, at least let me give you some kind suggestions and explanations:

You won’t have a lot of time to stay with him in love imagination because you have a lot of stuff to do like protect your family, support your parents, etc.

"love imagination" is an interesting phrase.

Although I want to follow the political correctness, we should take responsibility inat this age.

"in this age" means in the modern age, or in this time in the world. "At this age" means at the age of 30.

2. You can-not makbe sure whether the man is good or bad.

"cannot" or "can't" are both okay.

Maybe he is lying and flirting with you.

You should take care of yourself and alert this man.

"alert" isn't quite right here. "Alert" means to warn him that he is in danger. If he is very bad, you could alert the police so they know you need help.

3. You can find a nice partner in your lifesocial circle, not only in the internet.

You will have more ways to know a man if he is in your lifesocial circle.

Then it will decrease the probability that you will have been cheatinged.

Your grammar was correct, but it sounds like there was a mistake in meaning. "You have been cheating" means that you have been romantically involved with someone other than your partner. "You have been cheated" means someone has tricked you. "You have been cheated on" means your partner has been romantically involved with someone else.

The above are my suggestions and it is from a subjective perspective and is kind of one-sided.

Just pursue your true love if you really think he is thate one.

"The one" is a set phrase.