Currently, our inventory system does not support resolutions higher than 1920x1080. Therefore, please enable the "Fixed UI" option in your FiveM settings.
How to do that?
Step: 1
Open FiveM Client
Step: 2
Open settings. Top right.
Step: 3
You will see this menu.
Step: 4
Open Game option
Step: 5
Turn on Fixed-size NUI
And you are done. Close FiveM and open it again and you will be good to go!