i read that the only place to practice is indoors to avoid any complications with police.
i wanted to know if there is any other place where i can practice without causing any problems with police(last thing i want is problems with police).

currently you have only one field which is indoor and you pay for it per hour. Other solutions are not given at the moment. if you wonna play look in the event section. if you like to practice alone i dont see any chances at the moment for you.

Where can I rent something to play indoors? I'm already looking for a hall for around 4-6 people, but I don't have any idea where.

We're all newbies, so we thought we should first play alone before going to events toghether. Also it's more fun than getting stomped at official events.

you can go to Lasertag in Dietlikon
http://www.laser-tag.ch/airsoft

There you can rent stuff and the field for you.
it is okey to play with your friends but in the end you will learn more and faster from other player.

its great that you have a group of friends into airsoft. dont worry about getting stomped because i will go to oficial events alone