It is haram for a man to have a girlfriend and it is haram for a woman to have a boyfriend. The evil consequences and misery caused by such relationships are obvious to anyone who observes real life. For more, see the detailed answer.

There is no doubt that practicing oral sex outside marriage is prohibited and a grave sin, you have to give up this sin, regret what has happened and be determined never to go back to it. Do more good deeds to expiate and cancel out your bad deeds, do those things that will help you to remain chaste, and hasten to marry according to Islam.

It is not permitted at all for a man to shake hands with a non-Mahram woman.