I could only find three of them so far, and this one is my favorite. I could only find three of them, and this one is my favorite.

Or you could say, "I have only found three of them so far"

I couldhave only fiound three of them so far, and this one is my favorite. I have only found three of them so far, and this one is my favorite.

I don't think the original is wrong, but I agree with the tense suggested by @cmstevie. Because you used "so far" I know you are still looking, and the present perfect tense is the best to express that situation.

Some of its biggest advantages are that it's free, it hosts two meetings a week, and it only takes me around about 40 minutes to get to there. Some of its biggest advantages are that it's free, it hosts two meetings a week, and it only takes me around about 40 minutes to get to there.

Some of its biggest advantages are that it's free, it hosts two meetings a week, and it only takes me [round about 40 minutes] to get to there. Some of its biggest advantages are that it's free, it hosts two meetings a week, and it only takes me [round about 40 minutes] to get to there.

"Round about 40 minutes" is understandable, but there are more common ways to say this, including "about 40 minutes" and "around 40 minutes," so one of those would be preferable. You could also say "approximately 40 minutes" or "just over / under 40 minutes."

Although most people at this club are less confident at speaking than I am, I find it really gratifying to engage in a conversation with them and to learn about their job/s and backgrounds. Although most people at this club are less confident at speaking than I am, I find it really gratifying to engage in conversation with them and to learn about their jobs and backgrounds.

The set phrase "engage in conversation" works better here because you are conversing with many people about different topics. It is better to use a complete sentence because there is no need for a shortened form.

I never would have stumbled upon a Cchef or someone who has PhD in Linguistics in my day-to-day life, but at these meetings everything is possible. I never would have stumbled upon a chef or someone who has PhD in Linguistics in my day-to-day life, but at these meetings everything is possible.

I never would have stumbled upon a Cchef or someone who has PhD in Linguistics in my day-to-day life, but at these meetings everything is possible. I never would have stumbled upon a chef or someone who has PhD in Linguistics in my day-to-day life, but at these meetings everything is possible.

Everybody therewho comes has their own unique story to tell, so I'm always curious to learn something new! Everybody who comes has their own unique story to tell, so I'm always curious to learn something new!

I have two reasons to suggest replacing "there." First, it doesn't align perfectly with "these meetings" in the preceding sentence; and second, "there has their" sounds inelegant. Another option would be "who shows up." (I think "attends" or "participates" might be too formal.)

Actually, I don't even perceivsee these meetings as language learning anymore. Actually, I don't even see these meetings as language learning anymore.

Grammatically correct but 'see' or 'consider' may work better here

Actually, I don't even perceiveconsider these meetings as language learning anymore. Actually, I don't even consider these meetings as language learning anymore.

I agree with this suggestion from @cmsteive because "to perceive" is primarily visual or about our understanding of something, whereas "to consider" is more about our attitude toward something, how we evaluate or feel about it.

It's just fun. It's just fun.

This is a great idiomatic phrase, and you use it appropriately. My only caveat is that it doesn't align perfectly with a noun that you have already used: What is just fun? These meetings or language learning? On the one hand, the closest antecedent noun is "language learning" and that aligns. On the other hand you said that you don't consider the meetings AS language learning, so the subject of the sentence is "meetings." You could say, "They are just fun." You could also combine the two sentences "...anymore because I have so much fun." "...anymore because the whole experience is such fun" etc.