Now I like this site much more than it.

You don't need to specify "it" in this sentence, since we all know what you're talking about from previous sentences. You also don't need the "Now" because you're writing in the present tense.

I’m also using another language learning app, but it’s now more becoming amore like social media or like a dating app.

I don't think you can modify a verb directly with something like 'more' so I think you should modify the object of the verb using 'more', at least in this case.

I seldom get corrections, and many people don’t show their gratitude when I corrected their Japanese.

Since you are talking about in general here it might be better to keep everything in the present tense. If you want to keep the past tense then perhaps you can write "...show their gratitude after I corrected their Japanese."

Now I like this site much more than ithe other one.

It is a little unclear what the 'it' refers to here so maybe make it a bit more specific.

I’m using another language learning app, but it’s now more becoming has become more like a social media or like a dating app.

I seldom getreceive corrections, and many people don’t show their gratitude when I corrected their Japanese.

Now I like this site much more than ithe other language learning app.

using "it" is ambiguous. I'm assuming you are referring to the app you mentioned earlier but I'm not certain. Do you see what I mean?

I’m really happy when I canever I help someone even just a bit!

I’m using another language learning app, but now it’s now more becomingbecoming more like a social media or like a dating app.

This is a more natural word order.

I seldom get corrections, and many people don’t show their gratitude when I corrected their Japanese.

Keeping the present tense, as you use this for the part beforehand.

Now I like this site much more than ithat one.