when ever I join my friends sandbox server it my Garry’s mod closes after about 5 minuets does anyone know what to do.
so far I have validated game files, re installed Garry’s mod and re installed all the addons for my friends server.

You don’t need to have the addons installed on your machine to play on a server that has those addons. In fact, your game will be more stable the less addons you have installed, so I’d recommend trying it without addons and workshop subscriptions. Is it just your friend’s server that causes your game to crash?

no when ever I join I have to re download them they take forever he has over 100

What are your specs?

A8 5600K Black Edition
Corsair 4GB DDR3 1333MHz x2
Powercool 850W Modular PSU
MSI FM2-A85XMA-E35 Socket FM2
WD 1TB Blue Desktop Drive
Samsung 24x Sata Internal DVD±RW
Sapphire HD 7730 2GB DDR3

Someone else had this problem where the addons kept redownloading, their Garry’s Mod folder was set to read-only, stopping files from being saved inside. Check that