Before we go down the troubleshooting path for a problem that may not actually exist (as per @linub’s reply), I would recommend that you install a GPU monitoring program such as nvtop either via the Pamac GUI or by running in a terminal the command (as a normal user, not sudo): pamac install nvtop
Then run nvtop in a terminal and hopefully it should display the details of your GPU (if your system is set up correctly), including its fan speed.
If nvtop doesn’t see your GPU, or it does see the GPU but shows the fan not running even under a high workload/temperature, then please submit the output of inxi -Fazy as per the instructions in the following posts:
I’m no expert in GPUs, so this is probably where my assistance ends, but there are plenty of knowledgeable members on this forum who will be able to help you troubleshoot any GPU issues.
Edit: naughty me - forgot to put the dash in inxi -Fazy