It is good practice to ask you landlord or letting agency for permission to let someone else stay in your room, but unless your contract says you can't there is no reason you shouldn't invite people to stay for a few nights. It is important to respect other tenant's in your building and not make too much noise or make any extra mess - which I'm sure you wouldn't dream of!
If they come to stay in a hotel then it's not an issue as your landlord/agency need never know, nor would they be interested.
Your use of English suggests it is not your first language, having guests from abroad can be difficult if visas are required or there is some other political complication. This is an area too complex for non-professional advice (such as qsponge) and I would suggest you go to your embassy who will be able to give you help.