Translation:The thief steals paintings from the museum.
I wonder why the word "thief" is in the politics lesson.....oh, wait, got it
How come this is a present form without ending in -r? Which other verbs are like this appart from att veta?
Stjäla is an irregular verb (apparently, there has been an -r but it has changed for some reason). Other verbs without an -r in present form are e.g. gala (to crow), the verbs that have an -s in all forms (like finnas, finns, fanns, funnits) and almost all the auxiliaries (ska, vill, kan, måste...).
A tavla doesn't have to be painted, though it usually is. We also use tavla in compound nouns, e.g. whiteboardtavla, anslagstavla (notice board).