How can i make my bathroom faucet have increased cold water coming out

There could be many different reasons for reduced water flow. Other faucets on the same floor flow okay? How about the hot water at that same faucet? What kind of pipes do you have? Have you turned the shut-off valve below the sink off and back on? This may be a job for a detective plumber. Didn't they have a TV show about one in the 70s?

Could be the shut off valve needs to be replaced. To check - turn off the cold water, unscrew the hose from the valve. Place a cloth under the valve and turn it on slowly and see how the water pressure is. Could also be a washer or cartridge on the cold water side.

You can try some home-DIY methods: https://www.doityourself.com/stry/how-to-remove-calcium-buildup-in-pipes

Or you may just need to pay for repiping some or all of your house - gulp. Older homes experience mineral build-up in pipes in hard-water areas, especially if you're on well water, but any older home (50 plus years and older) will have this build up just due to time. Galvanized piping clogs up faster.

Take the screen out of the faucet and see if it has a lot of white stuff clogging it, it could be from mineral build up. Soak it in vinegar and scrub with a toothbrush.

You may have a clog

Hello. If it is just the cold water you may need to open the cold water valve up more. Check under the sink. You should have a hot water shut off valve and also a cold water shut off valve. Open the cold valve more. Good Luck!