Do I use "longer" correctly?
If not, could you please try to correct the sentence?
I like to make my work prefect.
So, I may need to spend a longer time to complete my work.
But, my work is perfect.
I find "[spend] a longer time" very unnatural.
I may have to spend longer ...
I may have to spend more time ...
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
"I may need more time ..." is even more economical.