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?

I suppose you mean ping spikes, It's the internet, you're losing packets from the server.

But if you're playing single player and it lags… It's your pc

A minuet is a 17th century.dance.

Bad internet is the main cause of network Lag, so - yes.