How many stars are between Milky way and Andromeda? Are there some stars between those two galaxies? In photos is only black. 

And if so, how many we could find there?
The stars between galaxies are called "intergalactic stars", and one study (2012) claims to have identified about 675 of them between the Milky Way and Andromeda:


  Now, Vanderbilt astronomers report in the May issue of the Astronomical Journal that they have identified a group of more than 675 stars on the outskirts of the Milky Way that they argue are hypervelocity stars that have been ejected from the galactic core. They selected these stars based on their location in intergalactic space between the Milky Way and the nearby Andromeda galaxy and by their peculiar red coloration.
  
  -"Rogue stars ejected from the galaxy found in intergalactic space", Research News @Vanderbilt (2012-04-30)