tunnel

  1. The train gets into the tunnel, runs through the tunnel and finally gets out of the tunnel.
  2. The train gets into, runs through and finally gets out of the tunnel.
    Which one is the correct sentence?

Both styles are possible, but “gets into” and “gets out of” sound odd here. You could use “enters” and “exits”.

Dozy,
Is this sentence correct?
“The train enters into the tunnel, runs through the tunnel and finally exits out of the tunnel.”

That is not exactly wrong, but you don’t need “into” or “out of”:

“The train enters the tunnel, runs through the tunnel and finally exits the tunnel.”