Iyi günler! 

Can someone please explain the meaning of -ken and -ce for me? My understanding is that they both mean "while". For instance, "sen yokken" means "while you´re not here". Or "düşünce" means "while thinking". I could be wrong but could someone please help me here. When would you use -ken and when would you use -ce? 

Thank you so much for your help in advance!

first of all düşünce doesnt mean "while thinking"

düş-mek: falling (v)

düşün-mek: thinking (v)

düşünce: thought (n)

DüşünCE hemen ayağa kalkamam. ( I can´t stand up right away when I fall )

Düşerken çantamı tutamam. ( I can´t hold my bag while I fall )

Düşününce yanlış yaptığımı anladım. (I got that I was wrong when I think about it)

Düşünürken birden sen aklıma geldin. (You came to my mind suddenly while I was thinking)

the difference is:

-ken is more like something "while happenning" but not done.

-ce is more like something "happened" or "after happening"

Wow! Thanks for the great explanation! It all makes sense now!!

Thanks again!