Hey there!

I wand to be able to play easy jazz standarts all on my own.. the melody and bass at the same time, using two hand tapping.

But i have such a hard time with the timming. I'm not a complete noob, but it was nearly impossible to play even two measures correctly, not even at half speed.

Any advice will be well appreciated!

I would say to work on them hands separately -- first learn how to easiely play the bass part, and then learn how to effortlessly play the melody part (and perhaps chord voicings, too).