Questions & Answers about Zwykle udaje mi się otworzyć ten sejf.
Why do we use udaje here instead of uda?
The word zwykle (usually) tells us this is a repeated, habitual action. Therefore, we need the imperfective verb udawać (conjugated here as udaje for 'it manages'). We would use the perfective uda for a single, completed success, like 'Jutro mi się uda' (I will manage it tomorrow).
Wait, if the action is repeated, why is otworzyć (to open) in its perfective form?
Even though the success happens repeatedly (udaje mi się), each time you succeed, you open the safe completely. In Polish, the infinitive following udać się or udawać się is almost always perfective because you are succeeding at completing the action.
Literally, how does the grammar of udaje mi się work in this sentence?
It translates literally to 'It usually succeeds to me to open this safe.' The verb udawać się is impersonal here, acting like an 'it' verb. The person who succeeds is the 'experiencer' and must be in the Dative case, which is why we use mi (to me).
Why is it ten sejf and not tego sejfu?
The phrase ten sejf is the direct object of the verb otworzyć, so it needs the Accusative case. Because sejf is a masculine inanimate noun, its Accusative form looks exactly the same as its Nominative (dictionary) form.