Please don’t do this:

2020-07-10 12:32:12 you: Hi
2020-07-10 12:32:15 me: Hello.
... time passes ...
2020-07-10 12:34:01 you: I'm working on [something] and I'm trying to do [etc...]
2020-07-10 12:35:21 me: Oh, that's [answer...]

This is the equivalent of calling me on the phone and then putting me on hold.

Please do this instead:

2020-07-10 12:32:12 you: Hi -- I'm working on [something] and I'm trying to do [etc...]
2020-07-10 12:33:32 me: [answers question]

You’re way more likly to get help much sooner, without making me wait. Instead, I can start thinking about your question immediately.

I know you’re trying to be polite by not jumping right into your question or request, like you would do in-person or on the phone, but chat is neither of those things. Typing is generally slower than talking, so instead of being polite, you’re making me wait for you to type your question, which is lost productivity.

The same applies to “Hi, are you there?” or “Do you have a minute?” or “ping”. Assume I’ll get your chat message at some point and just ask your question.

If you feel uncomfortable just asking the question, you can do something like this instead:

2020-07-10 12:32:12 you: Hi! If you're not busy I was wondering if I could ask a question.  I'm working on [something] and I'm trying to do [etc...]

Asking your question before getting an initial reply allows for asynchronous communication. If I’m away and you leave before I get back, I can still answer your question and you’ll get the answer when you return.