Alexander Sørloth is in 4th place with 16 goals, but he has no great chance of winning the top scorer award this season.
He actually has 17 goals in the fourth place. It's Raphinha and Ayoze Perez who have 16 goals each and sit in the fifth and sixth places respectively.
With 4 games left, I think Mbappe and Lewandowski will be fighting for the top scorer spot this season. They have a 1 goal gap, but Lewandowski could drop from the top scorer to second place if Mbappe can score consistently in the next 4 games. The competition between the two is very tight and I think Lewandowski will try to maintain his position at the top.
It's going to be a huge battle. It will probably gain some heat tomorrow during the El Clásico