steam reinstalling already installed games [SOLVED/FIXED]

[GHOST_ABK]

so i just downloadid destiny 2 due to our internet it took 4 days to download so u can think y i am so mad i download it after 4 days it worked i played the game loged out to sleep next day i open steam it opens i double click destiny 2 on desktop it says to me download destiny 2!!! i say ok np ill chose where its installed already i chose the place it says descovering existing files and when its done starts the whole freakin download againnn!!! i have proof of both already downloaded picture and same time steam downloading same thing all over againnn help this issue keeps happaning with other games as well i do not have a way to fix it plz help me !!!!

[Cathulhu]

https://support.steampowered.com/kb_article.php?ref=8379-RYIP-2998&l=

[GHOST_ABK]

i tried everything that page says it dont work

[GHOST_ABK]

so i found the solution its ez so bassically i downloaded the game on a different harddisk not a small portabele one but one thats inside pc so the prob was steam was only scaning the default folder of games and not the place where i installed the game so i shanged the default folder to the place where its installed and vollah it searched for existing files and there we go it was there