Could you give us a graphical illustration of vowel rules as they tend to be extremely difficult?

There are lots of instruction videos on Youtube, like these:

https://youtu.be/vhfCuYtnR2I for e/a suffixes (like de/da, ler/lar, den/dan, etc)

https://youtu.be/_FFQQAB2ds4 for i/ı/ü/u suffixes (like siz/sız etc, personal and ownership suffixes, etc)

For theory, this has been helpful to me: http://www.turkishlanguage.co.uk/vh1.htm 

Scroll down to the bottom for a simplified overview.

Hope its helpful.