Hi i need help pleas and thank you for your time

[mortal kiln]

so im trying to make a project so i put a billboard and a imagelable and then put an id in it so it follows the camera i wanna change the photo (decal) by making it if it detects the movmemnts walk run jump fall etc i need help i tried everything i could even asked my friend whos a developer even he couldent do it thankss