Hi everyone. I would like to ask a few questions: What happens, if I say, that we need to part our ways to the following dude?
What happens, if I tell him to wait and won't come back for long?
Does XP gets split?
Any special quests?
Any special dialogue options?

Any other special things I should know (which wouldn't happen, if I would play solo)?

If you decide to dismaiss a follower, you can send them back to where you first find them or a homebase you'll get during the game. If you tell them to wait, they wait. Rarely the game thinks you've abandoned them and sensd them home if it's too long.

You get the full exp for any kills they make.
Each follower gets their own quest that will be triggered by exploring with them. They also have a fair chunk of dialogue and give a unique perk that is different to each one.
You can only have one humanoid follower and one non-humanoid follower. The game is no worse off if you decide to solo, but you'll probably find places and things easier by having friends, if you get me.

xp goes to you
i told my follower to wait and forgot about him 4 ages and had to remember where i last seen him and he was still there
there are a side quests related to your followers, the follower i have at the moment

special dialogue does open up at certain points which then leads to the quest/s

hope it helps

Thanks for the information, that sounds pretty good.

What about, if I have a follower, and I meet another guy, that could be my follower, will I be able to postpone that dialogue options, and take the guy later?
Also, what happens, if the guy dies? Will he be dead, you can only play from the save, or something else will happen?

Your first question: if you already have a human follower say Boone, and you attempt to take Cass you will not be able to do so. You should, to make it easier if you wish Cass, send Boone back to Novac so you know where he is then you may take Cass. The same goes for ED-E or Rex - in the robotic sense.

EDIT: I should point out you can only have 1 human companion and 1 Robot companion simultaneously: Boone + ED-E; you can not have 2 of the same form.

Under any difficulty from Very Easy to Very Hard, your companion is automatically revived once combat has been complete; or you zone out/in of a location - a useful tip to know, In hardcoe mode if your companion is killed, they will not be revived.

Reno

Eh, the damn hardcoe mode... :/

Thanks for the information!

Keeping companions alive in hardcoe isn't as bad as it sounds, just be careful and keep an eye on them. A power armoured Veronica with her defensive boost perk is pretty much invincible.