I think my car's energy or electricity level may be low?

Problems have been occurring in my car, it's not recently. My car was a handi down and has about 80,000 miles on it. I drive a Honda 98 accord and the power seems low for some reason. For example, when I lower or raise a window in my car; my AC power reduces a bit and I think that the electricity shifts to the windows so it can work better. Another one, my windows down quite slowly. A few months ago, the battery or starter wasn't working occasionally but as of now, I think it's repaired temporarily; maybe this information could help.
Sorry, I don't really know much about cars but it's a problem I want to fix.

Should I buy a new battery/ starter or should I replace fuses or wires somewhere?

Thanks in advance

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