Elite Team came for on site troubleshooting with the following results:

A. Asus gt-ax11000 as router and dlink as modem, only technician windows laptop can get full 500mbps download speed. All my devices like Apple TV wired to Asus router, iPhone 16 pm, and even technician hand held device wired to my Asus router, all can get max around 150mbps upload speed.

B. Reset dlink and install 3.0.6 latest firmware, setup as bridge mode, same result with the above.

C. Reset dlink and setup as combo, Asus gt-ax11000 setup as ap mode, all devices can get full upload speed.

D. Reset dlink and setup as modem, use another Asus router of mine which is xt8 setup as router, same result with A above.

E. Use skyworth setup as modem, and use either 1 of the Asus router, same result with A.

Conclusion is suspecting Asus router firmware bug?? Need to check with Asus.

So stress doing all these simulations 

Btw, can some one shared if you are on 1gbps plan and Telekom device setup as bridge and running own router, please let me know what Telekom device brand, and router model assuming your up speed is 500mbps. If possible pm me your Unifi id so I can get elite team to check and verify.  Thank you so much.