Longsword Expert

You have mastered the longsword, granting you the following benefits:

A +1 to your AC while wielding a longsword with two hands

Your damage die for two handing a longsword is still a D8, and you gain a +3 to damage

Any effects that would apply to a longsword while wielded with on hand apply while two handing, e.g. dueling fighting style

The weapon is not treated like a great weapon while being two handed, so things like great weapon master would not apply