It's not your son's fault - you need to control other people's children instead
Especially if you've invited them around your house. And especially if they're doing things which are unfair on your child. As far as possible, you let their parents intervene - but if they aren't on hand, or they're distracted, or they just haven't noticed, then you can and should do it.
So I'm going to challenge your concept of the problem. Your problem is not that you need to teach your son what to do, because your son's actions are reasonable. You are letting that other child mistreat him, seeing it happen, and taking no action. So your son is learning that parents won't intervene, and he's having to take action himself, and the only thing he knows at that age is to retaliate. The reason he's fighting/biting is because you haven't stepped in. He then gets extra upset because it's unfair that he's the one being told off.
Similarly the other child is also learning that there is no sanction if they do this to your son.
The other child takes a toy off your son? Take it off them and give it back to your son, and say "wait a little bit, baby, you can have a turn after him".
The other child is blocking the ladder up to a slide? Say "come on darling, up you go now". Or "Are you not wanting to slide after all?" If they're hanging off the ladder, that's actually not safe. Children climbing up the slide is the other common issue.
If the other parent isn't anywhere around, the responsibility is on you to do that. And if the other parent is around, they should expect you to do that, just as you'd expect them to intervene if your child is mistreating theirs and you're not on the spot. As parents, you put on a united front when children are taking other children's toys, or doing things on a playground which are potentially unsafe.
Don't forget that this goes both ways too. You need to be stopping your son from doing the same things; and if you happen to miss it, you should expect someone else to step in.
Of course some parents can't deal with the fact that their precious darling might be doing something harmful (or dangerous) and needs to be set boundaries. If that's the case, they're entitled idiots and not people you want to be hanging around with. No loss.
And if this is happening at a kindergarten where you're leaving your son, then I suggest you need a better kindergarten. If they don't have enough staff to monitor who's stealing whose toy, then they also don't have enough staff to monitor who's eating that toy, or stuffing it in their ear, or stuffing it into another child's ear, or anything else fundamentally dangerous.
Of course you should also be teaching your son not to fight or bite, and to wait his turn for the toy without getting upset, as you're doing. It shouldn't be his first answer when something doesn't go his way. But violence always remains everyone's last answer when they're pushed too far, and as an adult you should be de-escalating the situation before it gets to that point.