I knewmet him several weeks ago from a chatting app.

I knew him for've known him since the first day Iof useding that app and we had a phone call.

His voice was so young and so nice and I really liked it.I really liked his voice because it sounded so young and so nice.

After several days of talking, we got to kneow each other more and then he sent me hisa selfie.

He is well-built with broad shoulders and, has an oval face, an up-turned nose, beautiful sleek hair and bushy eyebrows.

I can feetell that he is always immaculately groomed.

SomeAt times, I am jealous of his long eyelashes.

We talked almost every day and I feelt that we could talk for continual 24 hours, if there were no time lag.hours.

We hadcould discuss endless topics, but we also enjoyed companionabl the silence.

Too mMany people seemed to believe that silence wais a void that neededs to be filled, even ifwhen there's nothing important wasto saidy.

Every time I talked to him, I feelt that I could escape from the pressure and the hardship in my life.

And every time after I huang up our callthe phone, I feelt refreshed and energetic.rejuvenated.

My best friend

This is fine, obviously, but to me, it's odd to describe someone whom you only met a few weeks ago as your best friend. The main exceptions that I can think of involve either small children or joking around (with a bit of exaggeration):

- "They've gotten on really well since the first day of kindergarten, and now they're best friends."
- "He and I have very similar interests and habits, so we hit it off and are best friends now."

"A close friend" might be better. Another native speaker might have different thoughts though.

I knewmet him several weeks ago fromon a chatting app.

"Chatting app" exists, but this sounds more natural to me.

"Know" in the sense of "become acquainted with" does not sound idiomatic here.
- It tends to describe a continued state rather than a specific event; specifying a (recent) time and placing it where it would be implicitly associated more with the verb "know" is a bit odd here.
- We can still associate "know" with a specific time, but in my experience, that happens mostly in the context of a longer time frame, and "already" is somewhat implied: "I knew her two years ago from school, and she was very different back then."
Were you thinking of "認識"? "Meet," "come to know," etc. are likely more appropriate as translations when the object is a person.

I knew him formet him the first day I used that app, and we had a phone call.

After several days of talking, we knew each other more and he sent me his selfie.

Sometimes, I am jealous of his long eyelashes.

We talked almost every day and I felt that we could talk for continual 24 hours24 hours straight, if there were no time lag.

"Time lag" is unclear. Do you mean "time difference" (like being in different time zones), or lagging on your computer?

We had endless topics to talk about, but we also enjoyed a companionable silence.

"We had endless topics" is fine, but it's clearer and sounds better with the clarification "to talk about."

Too many people seemed to believe that silence wais a void that neededs to be filled, even if nothing important wais said.

This is presented as a general truth, so the present tense is more appropriate.

And every time after I hung up on our call, I felt refreshed and energetic.