I just updated the router to the latest firmware version but still wont work.
In this attachment you can see that only in the Guest-network the dhcp work correcty.

 

  @AdminCat 

 

there have been many problems with DHCP on all tp-link routers for a long time, this should probably be solved with the latest firmware upgrade, so try adding version 2.1.2 to your router, you can find it here.

https://www.tp-link.com/en/support/download/er605/v2/#Firmware

 

 

i just updated, but the problem still exists.

  @AdminCat 

hmmmm, when you create VLAN do you enabled interface on router conneted to the switch?

  @shberge 

 

I think i have done it right.

This is the working LAN:

This the NOT working LAN:
 

 

  @AdminCat 

 

yes, it looks like this, have you tagged the switch with vlan 10 and 20? or are the access points connected directly in the router?

  @AdminCat 

 

sorry but I see you have an unmanaged switch now, you must have a managed switch to be able to use vlan,

 

 

The switch is a unmanaged one. Does a unmanaged switch remove the vlan tag? Do i need a managed switch to merge VLAN 10 on port 1 and VLAN 20 on port 2 on the uplink port 3 to VLAN 10|20?

  @AdminCat 

 

yes, you should have a switch that you can manage, alternatively you can connect the access points directly to the router, then vlan will work on WiFi

 

 

  @shberge Okay i replaced the unmanaged switch with a smart switch and configured the ports as followed:
Port 1 = Uplink VLAN 10|20
Port 2 = access point 1 VLAN 10|20
Port 3 = access point 2 VLAN 10|20
 

If i connect to the SSID hybrid, i get VLAN 10, if i connect to SSID Guests i should get VLAN 20.

"It is an old switch, i will replace it with tp-link" ;)