Some strings are not translated because they are not currently available on Crowdin. I'm talking about:

• Presets in Superflat Customization > Select a Preset that are in English and aren't translatable on Crowdin. fixed in 1.11
• The text in debug menu (F3) is also not translated. _{Mod edit: It's a debug screen, only for testing purposes, not for normal gameplay.}
• The biomes in the biome slider (Customized world) also doesn't have translation. Invalid according to grum.
• The Elder Guardian as well – Unable to find this one grum.
• Default empty world name is "World" Invalid according to grum.
• Commands in spectator mode ("Press a key to select a command, and again to use it.", "Teleport to player", "Teleport to team member", "Next Page", "Close menu") fixed in 1.11
• Options -> Graphics settings -> "Entity Shadows" Fixed in 1.9
• New 1.8.2 / 1.8.3 Statistics (MC-77880) Fixed in 1.9
• Potion item does not translate since the removal of data value Fixed in 1.9
• The new error message added in 16w02a: "Invalid damage property. Please pick in [Valid Blockstate Numbers]" Message got removed
• The new debuging messages, for example "[Debug]: Reloading all chunks" fixed in 1.11
• A number of subtitles: Are at cowdin, but not translated in game yet Fixed in 1.9.2
• Video settings: chunks and FPS fixed in 1.11
• "Color" on dyed armor in advanced tooltips fixed in 1.11
• "NBT x tag(s)" in advanced tooltips fixed in 1.11
• "Unable to load world" screen is not translated at all (outside of the cancel button) fixed in 1.11