I'm trying to make a combo system with a timer?

So what im trying to do is make a combo system with a timer kind of like Dragon Ball Ultimate Tenkaichi you press mouse button 1 enough times without getting hit and it does a special move to end the combo but if you don't do it in like 5 seconds the combo stops and then ends(combo only begins on a player though)

Please help I've been stuck on this forever now and I'm really rusty. Examples/Templates would be much appreciated

PS you might have to dumb it down a little bit as I've just come back to scripting on roblox after like 2 years.