A 5th gen iPod Touch can only go to iOS 9.3.5.
Your 5th gen iPod Touch is too old and has internal hardware too underpowered to be able to effectively run even the baseline features of iOS 10 OR 11.
Sorry.
The “new” ( 2-1/2 year old ) 6th gen iPod Touch is still available and is very capable of running iOS 10 or 11.
Good Luck to You!