GT King Firmware update? Other system? PLEASE Help!

Alex1990

Hello,
i bought a GT-King a long time ago and never done a firmware update as i think you need to do it manually.
I struggle a lot with Neflix / Disney+ and IPTV as i get errors in the Video, no sound or problems with the Streaming or freezing and restarts of the box inside these Apps.
Cause of that reason i want to bring the Box onto the newest firmware.
Can somebody tell me where and what the right firmware is to download and how to install or find a guide?
Can i install the latest version right away or do i need to update the firmware step by step every version?
I read something about a seperate System on the SD Card? is that possible on the GT-King Version and how to set that up? And is that more suitable for my needs?

I really need the box only for these Apps

1. Netflix
2. Disney+
3. Amazon Prime
4. IPTV
5. Browser
6. VPN App
7. Google App store

But simply it´s a video only box..
I´m a student so i couldn´t buy and don´t have the money to buy a new box so hopefully you guys could help with the questions i have!
I add a picture of the back of the Box for all the details!
Thanks a lot in advance for everybody that takes the second to help and hopefully you understood as english is not my native language :)
Thanks!

Details:

Modell:
GT King
Version:
9
Kernel Version:
4.9.113
Build:
901K0

beelink

Hello,
Our TV BOX has OTA push wireless upgrade function, you can find the wireless upgrade in the settings and update the firmware. The firmware released on the forum is for users who fail to upgrade wirelessly. USB manual update does not need to be updated step by step. For the SD card independent system, you can refer to the Forum CoreELEC section and the EmuELEC section. Some applications that cannot be installed normally can be found in the appmarket, and these apps can be used.