The Best Love

I'm always impatient, but I steadfastly love you. This is a good translation by meaning
做事总三分钟热度的我，却爱了你这么久，

The me of just having a three minute passion on things, still love you for so long,

I'm always forgetful, but I clearly remember you.
平常总健忘丢三落四的我，却把你记那么清。

The scatterbrain that I am most of the time, still can remember you so clearly.

I like you not because your looks, but the incomparable special feeling that you give to me.
并不是你长得好看我才喜欢你，而是你给我一种所有人都给不了的感觉。。。

Not because of your beauty that you are liked by me but the feeling you impart for me that all others cannot...

The best love is not forever love but simply is together two
其实最好的爱情，没有天荒，也没有地老，只是想在一起，仅此而已。

By direct translation, Actually, the best kind of love is when heaven never becomes barren and earth never grows old, only when we want to be together, then we are one.  Merely this and nothing more.

By meaning, The best is not love eterne but to be together and this is all.

Best Love

I'm always impatient, but I steadfastly love you.

做事总三分钟热度的我，却爱了你这么久，

I'm always forgetful, but I clearly remember you.
平常总健忘丢三落四的我，却把你记那么清。

I like you not because of your looks, but because of the incomparable special feeling that you give to me.
并不是你长得好看我才喜欢你，而是你给我一种所有人都给不了的感觉。。。

The best love is not forever love but simply is to be together as two

The best love is not love that lasts forever, but simply to be together as one.

We can understand your original sentence.  In English we usually say 'to be together as one', but depending on your chinese meaning/feeling maybe two is correct for you.
其实最好的爱情，没有天荒，也没有地老，只是想在一起，仅此而已。