All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
If your life with your wife is as you have mentioned, full of arguing and there is no way for reconciliation, then you can keep the bond of marriage with her and take a second wife if you are able to deal justly (with them) for it is a prerequisite for polygyny as explained in Fataawa 95416 and 81469. This is the first option.
The second option is that you divorce her and marry another woman. But, if you keep things the way they are now, then this will lead to much corruption for your religion and worldly life as well. This is not how wise and sane people behave. You have to beware of letting your eyes wander freely at women who are unlawful for you or taking girlfriends. What benefit will you gain if you committed a sin - to enjoy your life as you claim - while the end of that will be great regret in this life and on the Day of Resurrection?
So do not be deceived by the deception of Iblees (Satan). Allaah The Almighty Says (what means):
• {O children of Adam, let not Satan tempt you as he removed your parents from Paradise, stripping them of their clothing to show them their private parts. Indeed, he sees you, he and his tribe, from where you do not see them. Indeed, We have made the devils allies to those who do not believe.}[Quran 7: 27]
• {Indeed, Satan is an enemy to you; so take him as an enemy. He only invites his party to be among the companions of the Blaze.}[Quran 35: 6]
As for that married woman, you have to keep away from her and beware of having any relationship with her so that you do not turn her against her husband, as that is a grave sin. You may refer to Fatwa 92056 about the prohibition of spoiling the relationship between a wife and her husband.
Allaah Knows best.