Learn English – To talk about a hobby, should I say “I like swimming” or “I like go swimming”

As the link you quoted says, it is a very small difference. It's not really a difference in meaning, but in implication. Try this example:

I like eating ice cream.

Emphasises the action or experience

This implies that the act of eating is most enjoyable. The action of eating it is the best part of the experience.

I like to eat ice cream.

More emphasis to the results

This indicates that the ice cream itself is the best part. As in, the result of having ice cream in you is what you enjoy!

Don't worry about the difference too much when you are speaking. In casual conversation, they are pretty much interchangeable.

Infinitive: To forget to do something is to fail to do that thing because your memory failed you. E.g., forgetting to take your pills means that you failed to take your pills.

Gerund: Your memory failed you, but you didn't necessarily fail to complete a task. E.g., "I forget meeting him." There was no task of meeting this person that you failed at; you simply don't remember the meeting that took place.

But note that "I forget meeting him" isn't particularly elegant-sounding English. People would more likely say, "I don't remember meeting him." But "I'll never forget meeting him" sounds perfectly fine.