Grammarly is a useful tool, however there is only so much one can expect from grammar checker software.

I will point out a few examples:

They are a lot of outstanding work involved in recent developments

This is a bad sentence. If I understand correctly, this sentence should read: ''There is a lot of outstanding work involved in recent developments.

When I first heard of the telegram messenger, I was a bit anxious because it raves were a trending topic back then so, I had to grab it.

I am not sure I understand what you mean, it looks like there's some sort of typo or missing word; this sentence could be interpreted in multiple ways, so there is really no way of knowing for me. I guess you meant to write: ''When I first heard of the telegram messenger, I was a bit anxious because its raves were a trending topic back then, so I had to grab it."

They are essential topics about telegram messenger that I which to discuss in today’s article.

Again, this sentence doesn't make sense due to typos and misspelled words. This sentence should read: ''There are essential topics about the telegram messenger app that I wish to discuss in today’s article."

I hope you will find this comment useful.