How To Downgrade My Phone?

Hello All,
I've owned Samsung GALAXY Star Plus GT-S7262, after I bought a new phone, I was given my old phone to my father. The phone is just used for calls and SMS, the phone is already slow and lagging and touch also lagging. I want to minimize the functionality of the phone to become more fast and not lag anymore, like uninstall the system applications like Galaxy Apps, not used system tools, things like that. How to do it?
Thanks in advance

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