We have managed to gain some time, but there are frozen reindeer on the tracks! We need to help them!
Talk to the herder and she will lead you to a special rock formation.

Break off the rock and roll it straight to the fire.

Now push the rock in the place between those frozen reindeer to melt them.

The herder asks us nicely to help find 4 other frozen reindeer. Follow the traces and you will easily find them.
Just repeat the steps that we have learned from the herder and the reindeer will be saved.

When moving the stone to the third found reindeer, make sure to push the stone, rather than pull.

To get the stone to the last reindeer can be problematic, as he is stuck on a floating iceberg. Thankfully, this lumberjack offered us to build a bridge, if we clean his igloo.

Then break off the stone, heat it up and push it towards the reindeer.

Return back to the train and talk first to the herder and then to Mr. Thanks, so we can proceed.
🌟 👑 TREASURE PART
To see what a correct answer to open the gate is, peek here.