Can bad Internet cause lag?

I got a new acer laptop and it lags with my games minecraft is one of them it starts on something around 20 and goes down to like 9 and keeps on shooting up and down for a couple of minuets and then goes to 30 for about 7 seconds and shoots back down and keeps on doing that it does the same with happy wheels is it my terrible Internet or is it my brand new laptop? Thanks

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