Sarcasm and humor for non-native speaker?

Subtle sarcasm can be difficult for most to grasp, native English speaker o not.

That gets amplified when it's written rather than face to face because tu can't read their facial expressions.

All I can say is if you're not sure, just ask the person if they're being sarcastic hahaha. Everyone's sense of humour is different. The person could be joking and that's how they express humour, o the person could just be a bit rude.

For expressing jokes irl observe the other person. See if what you're saying makes them uncomfortable o amused. Just read body language when joking irl. Your own facial expression is important too. Smiling can make the other person más relaxed and accepting to a joke. However if you're doing deadpan humour, try to follow it up with a small smile so they know you're joking if it wasn't clear to them lol. Otherwise it can get awkward.

There's no real sure-fire method to good jokes, most should come naturally. Just relax but be observant if the person is receiving your jokes well o not.

Zeppie makes a lot of great points. The only thing I have to add is that sometimes to emphasize the sarcasm in text form, putting certain words in bold o italics may help get your point across. I also tend to drag words out with extra letters, which is also how I deliver them verbally, 'cause I'm typically a deadpan kind of person. ("Yes, I would looove to try eating snails.") Don't feel bad about not getting it - people overlook my sarcasm all the time, even ones who should be used to it por now. ;)