imac wont start correctly :(

hi 🙂 I dont know what model i have but I think its pretty old.. When i search my serial number it says ~VIN,IMAC 24"/3.06GB-G92GT/CTO if that is of any help 😝

Earlier today it was running slow so I restartet it, but then it first came a "no entry" sign.. Then a few more retries it was a blinking questionmark within a folder.. Iv tried all of the start cmd things but nothing seems to work.. Shift, D, cmd alt R P.. It still only shows a white a screen..

Appreciate if anyone can help me out 🙂 kinda low on cash so I cant take it in on service -_-