I upgrade my pc windows 7 64bit to windows 10 but I need windows 10 32bit... What to do now? If I do

Well you should have installed Win7 32bit then upgraded. Or purchase more ram. What product key do you have?
 
While you won't need a 64 bit version of Windows for a machine with 2GB of RAM, the 64 bit version should run just fine on your PC.
 
I assume you have reasons for staying with 32bit (hardware attached an issue likely)

Download Windows 10 32bit from the website or even better, stay on Win 7.
For now, Win 7 will continue to run fine and you avoid the many pitfalls of Windows 10.

New is not always better even when offered FREE.