OVAS to The seven deadly sins?

I watched the first and second season plus the 4 episodes that are on season 2 on netflix. Are these 4 episodes part of the Ovas? And how many ovas are there only 2 episodes of ova known to me (apparently around Ban) But recently I heard there were a total of 8 or 9 ovas so I wanted to ask how many there are and where I can watch them. Come before the third season. Otherwise I would start the third season (in English. Since netflix doesn't have it yet) (so sub in English) Thanks in advance

"The Seven Deadly Sins' has a total of three OVA episodes.

All three OVA's can't be viewed legally here.