I hope that most of you will have the game installed on a fast SSD so that everything can load quickly and smoothly.
But as we know SSD storage space is still significantly more precious than HDDs and so every gigabyte matters!
This guide will show you how to delete language files that one doesn't need. This is actually functionality available to developers through Steam but sadly it's rarely being utilized... :(

I recommend first moving those files to the Recycle Bin - in case something goes wrong you can just simply restore them without having to redownload everything. After verifying that the game still works without problems you can permanently delete them.

First go to your Steam Games folder (by default C:\Program Files(x86)\Steam\steamapps\common) and locate the game. Then dig deeper until you reach this destination, in my case: E:\Steam\steamapps\common\Uncharted Legacy of Thieves Collection\Uncharted4_data\build\pc\main\sound1\streams\speech
Delete every file there EXCEPT for the languages that you want to use - in my case I only left english.psarc in place.
After that repeat this process for the speech-tll folder (that's the Expansion/DLC).
Full path: E:\Steam\steamapps\common\Uncharted Legacy of Thieves Collection\Uncharted4_data\build\pc\main\sound1\streams\speech-tll

You can also delete the executables that you don't need, depending on if your CPU supports AVX. Mine does and so I got rid of u4-l.exe and tll-l.exe in the game's main directory .
Otherwise delete the two other ones.

In the unlikely case that the game is further patched these files might be restored so these steps would have to be repeated.

I hope that this short guide was able to help you reclaim some precious disk space!
Take care!