"Próbuję rozmawiać!"

Translation: I am trying to talk!

[daylamay2]

Seems like the verb 'to try' is similar in many languages

[kjettern]

This one will come in handy in conversation with my future Polish wife.

[Neil395069]

You can try, but you won't succeed. Trust me :D

[Walkinthedog]

The boss would like to speak to you, speak slowly, I can't understand you when you speak Polish etc.
I believe it's more formal than talk here.

[Matthew_Phelps]

Yes it can be used formally but also very informally:

• "Son, speak up!"
• "Hey!!! Who spoke?? I heard you.."
• "Speak here into the mic"

[Walkinthedog]

I am trying to speak would also fit the bill as it is more often used talk.

[Jellei]

It's accepted.

Is 'speak' used often for having a conversation?

[Matthew_Phelps]

Yes. I would in fact label it just as common as "talk" in this context. For example, if you're really irritated with somebody:

"AHEM, who told you you could speak?? I'm trying to talk here and no one is letting me!"

[Walkinthedog]

I hear you speaking and I concur. Talk about getting confused if you don't speak English, when you wish to talk to someone who does/

[Walkinthedog]

That's any married man when his sister in law comes to visit his wife. An exercise in futility.