My manager keeps on approaching me on whatsapp or emails for work during the weekends. I am a hardworking and dedicated employee but that doesn’t mean I have to make myself available all the time for my company. How to convey this to my manager?

If it’s an occasional thing, check the priority of the work. Take a call depending on the context of the message, such as whether a task or question can wait until Monday to be addressed. If it’s a regular thing I suggest you talk to your manager politely.