config wireless client mode

hi,

i´m trying configure my: BaseBox RB912UAG-2HPnD als wireless client mode.

like to do:
internet ↔ Router/AP/Wlan(device1) ↔ Wlan ↔ BaseBox ↔ some LAN Clients

tried:
http://forum.mikrotik.com/t/routerboard-configuration-as-wifi-client/145843/1 and https://administrator.de/forum/mikrotik-als-gast-wlan-client-440501.html

steps done:
bridge → ports → delete wlan interface
connected to wifi → config security profile → B0:95:75:EB:5A:14@wlan1 established connection on 2437000, SSID Einhornaufzuchtstation
ip → dhcp client → interface → set wlan1 → dhcp client changed by admin → shows only status searching…

problem:
don´t get ip by dhcp server (device1) → so i set ip manually → ip → adress → 192.168.50.30/24 interface wlan1 / communication to wifi now running → ping: 0 192.168.50.2 56 64 4ms

so next step doing nat so my lan clients can connect to the internet from device1:
ip → firewall → chain srcnat + out interface set to wlan1 → lan clients can´t connect to internet devices/net

question 1:
how to troubleshoot/fix dhcp request/get problem?

question2:
how to set firewall nat correctly to make internet for lan clients available?

thanks a lot
stefan