My GMOD server is very messed up

Hello I recently made a GMOD Prop Hunt server. The first problem is I can get on my server but my friends can't. Is it my portfowarding becuase I used the port 27015 to 27015 but I only did it on UDP. The server shows as 192.168.1.74 but says my public ip is supposed to be 99.30.171.92 but when both are on there 192.168.1.74 is being used but in the start up it says 99.30.171.92. How can I solve this? No one can join but I can and It is really annoying. This is my first time on these forums and I really need answers becuase I have tryed everything and I need help from someone who knows what they're doing.

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