My cat strains to pee after neutering, but still pees. Is it normal?

HI there! I'm so sorry to hear about Gulbi's troubles. Although there can be some discomfort following a neuter, I would definitely keep a close eye on Gulbi. Male cats can have a condition where they are unable to pee. Often we will say a cat "is blocked". This is a medical emergency because when an animal cannot urinate, it can back up their kidneys, and cause them to become toxic, very sick, and possibly pass away.
I would continue to watch Gulbi as you are. He needs to produce a nice stream of urine, and large quantities of urine in the litter box. If there is any straining, especially frequent straining, or just tiny circles of urine in the litter box, then he should be evaluated by a veterinarian. He may need some pain medications, and if he already has some, he may need some additional ones.
It may be helpful to put Gulbi in a small room by himself for a couple of days, like the bathroom, with his litter box. This way you can keep an eye on his litter box and the amount of urine he is putting out.
If he is licking at his neuter area, I would pick up a cone from the pet store. Also important is to bring Gulbi to see the vet if there is any swelling, redness, or discharge, like pus, around his neuter site.
I hope you find this answer helpful. Best of luck!