pixel_player467974265 This help site has everything you could possibly want to know. It is run by a player, and has no affiliation with PF other than the permission to use their data.
Explore the menus, and if you click on the little figure icon in the top right corner, you open a settings page, where among other things, you can put in your current game level to get more specific content.
As for the Titanic, as @Nitrum has said, it’s a long term special ship within the game. It has the potential to be with you for many hundreds of levels, and upgrading it can be viewed like a game achievement, as it can not be speeded up with gems.