Running a server with LTE R7100G

Hello, For some time I try to run a server on my network in order to reach for example my NAS or my security camera's from another location (so outside my own network). To my opinion I tried everything possible:

- I have a DDNS address (No-IP and also Netgear) and entered it in the router

- I tried to put the server in the DMZ

- I forwarded the port for the server

I use this modem/router with a SIM card only (4G network)

I do not come any further. I suspect that my provider (T-Mobile 4G network) is blocking this, but before I start to make a lot of noise there, is there somebody having an idea what I have missed or did not do? Thanks