Can you combine/import several adventures into one game?

I'm planning on running Phandelver and Below: The Shattered Obelisk and want to also include Forge of Fury in the same game. Can I import that adventure into PBtSO or do I have to run FoF as a separate game? If I can import it, I'd love some instructions on how to do this please.

If they are both MODs, you can't import them (unless you are a pro subscriber and use the Transmogrifier).

I intend to Pro subscribe so curious how the Transmogrifier work?

When you click the transmogifier button, it gives you the option of choosing 2 campaigns with one selected by default (the one you are in). It shows all files in each  campaign, and you can simply drag things from one campaign to another, whether they are maps, characters, etc. Once dragged from one list to the other, the item now exists in both campaigns. You can drag in either direction.

You might not want to do that as you can get too many pages and character sheets, which can kill performance. Your players will only have to switch once when they reach the end of game one. You can move their characters etc. into the other game with the character vault or the transmogrifier. You can even go back and forth if that is how you wind up running the game.

Forge of Fury is an Add-on so you can add it to Phandelver and Below. You do not need to be a Pro subscriber to add it to your game.  Modules cannot be added to existing games, except as noted above via the Transmogrifier, with the above stated issues.  Add-ons can be added to existing games. 

Thanks for clarifying that Gauss!