Started learning CW but 20 wpm seems pretty hard

Hi everyone

Yesterday I started learning CW on lcwo.net but I'm struggling with which speed to choose. Default settings are 20 wpm and effective speed is set to 15 wpm with a 600Hz tone. I changed effective speed also to 20 wpm but it's quite hard now.

I'd like to ask what is actually the best speed to learn CW in order to hop on bands right after learning, be able to understand it and not to annoy anyone for being to slow.

I'd be grateful for any advice.