Learn Swedish: Vi jobbar inne på lagret idag. - We work inside the warehouse today.

Because the action is happening in a fixed location. Inne is a positional adverb used when you are already staying inside. If you were moving into the warehouse from the outside, you would use the directional adverb in instead.

Why do we use på after inne instead of i, since they are inside?

It is common in Swedish to use på for workplaces, departments, or specific functions, like a warehouse (ett lager). Even though you use inne to emphasize being indoors, the standard preposition for working at a warehouse remains på.

How does the word lagret (the warehouse) get its ending?

It comes from the ett-word ett lager. To make it definite (the warehouse), you add -et. However, to make it easier to pronounce, the e in lager is dropped, making it lagret instead of lageret.

Can I move idag to the start of the sentence?

Yes, you can say Idag jobbar vi inne på lagret. Just remember the V2 rule! Because the time word idag takes up the first position, the verb jobbar must stay in the second position, which pushes the subject vi to the third spot.