The ghosts can't be fought in their current forms. To beat them you have to see them and you can when you get a Silph Scope. You get the Silph Scope in Celadon City somewhere (No spoilers unless u want them)
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Use the Silph Scope. You get this by defeating Team Rocket, when they steal it.
You have to get the silph scope. To get this you must go to the game corner in Celadon then go to the poster at the back to reveal the team rocket hideout, you must then battle through the hideout then beat the leader who will give you the silph scope so you can see ghosts, you can then defeat the ghost blocking the way and continue up the tower.
You need the Silph Scope to see it, then defeat it.
you need to find the silph scope this will reveal the ghost to be a marowak you can then defeat it
Get the Silph Scope from the Celadon Rocket Hideout, then ascend to the top of the Pokemon Tower. Then, you'll be able to identify Marowak and defeat it to lay it to rest.