He shared it, and I thought it was exactly what I was looking for. He shared it, and I thought it was exactly what I was looking for.

Use a comma in combination with "and" to separate two independent clauses. This site goes into some more detail: https://lifehacker.com/remember-the-fanboys-rule-for-proper-comma-usage-1755944556

I was trying to find a website where I could post my thoughts and ideas and others canould help me. I was trying to find a website where I could post my thoughts and ideas and others could help me.

You want to use the conditional “could” both times in this sentence.

My personal goal is to learn how to write better, find new vocabulary, and correct my grammar. My personal goal is to learn how to write better, find new vocabulary, and correct my grammar.

A comma is generally after everything in a list before the final "and".

I have problems trying to connect the sentences and I do not need to learn how to write perfectly, but I would like to learn native ways to express myself. I have problems trying to connect the sentences and I do not need to learn how to write perfectly, but I would like to learn native ways to express myself.

I have problemdifficulty trying to connect the sentences, and I do not need to learn how to write perfectly, but I would like to learn native ways to express myself. I have difficulty trying to connect the sentences, and I do not need to learn how to write perfectly, but I would like to learn native ways to express myself.

I would try to avoid combining 3 or more sentences using conjunctions. It's easier to read when you split them up in separate sentences. I would rewrite the sentence like this: "I have difficulty trying to connect the sentences. However, I do not need to learn how to write perfectly, but I would like to learn native ways to express myself."

I have ptroublem trying to connect the sentences and. I do non’t need to learn how to write perfectly, but I would like to learn native ways to express myself more like a native speaker. I have trouble trying to connect the sentences. I don’t need to learn how to write perfectly, but I would like to learn ways to express myself more like a native speaker.

In place of “I have problem trying “, you could say “I have difficulty” or “I have problems” or “I have trouble”, but you wouldn’t use the singular “problem”. I split your sentence into two for stylistic clarity. “learn native ways” sounds unnatural in this context, I provided an alternative which will be understood more clearly.

However, any correction it is welcome. However, any correction it is welcome.

However any correction it is welcome. However any correction is welcome.

You don’t need the “it” in this sentence.