how to pump up schrader valve bike?
From these three, which one you have?

Case ①:



Schrader valve

Check if the inner part (valve) is properly installed (tight enough). If is and still loose air — you need to change the valve or the inner tube, the problem is with one of them.

Case ②:



Presta valve

You need to unlock the valve before pumping, or you will pump air only into you pumps' hose. After pumping don't forget to lock the valve back.

Case ③:



Woods (Dunlop) valve

Very old system. Check inner parts (steel needle and rubber tube) for damages, rubber tube can degrade flexibility with years → air loss.