Learn Turkish: Onun profilini engelleyip duruyorum.

This sentence uses the continuous repetition compound verb: Verb + -(y)ıp + durmak. The main verb is engellemek (to block). We take the stem engelle-, add the buffer -y-, and then the suffix -ip. Finally, we conjugate durmak in the present continuous tense as duruyorum. Together, they form the meaning 'I keep on blocking.'

Doesn't durmak mean 'to stop'? Why does this sentence mean 'I keep on blocking'?

It is definitely a paradox for English speakers! While durmak literally means 'to stop' or 'to stand', when used as a helper verb after the -(y)ıp suffix, it completely changes its function. It indicates that an action is stubbornly or continuously repeating. You can imagine it as 'I block his profile, and I stand by that action over and over.'

Why are there two -i suffixes at the end of profilini?

The word profil (profile) has two different suffixes attached here. The first -i is the possessive suffix linking it to onun (his profile). The second -i is the accusative case marker, which is required because 'his profile' is the specific direct object receiving the action of 'blocking'. The -n- in the middle is a buffer letter, which is always used when adding a case marker to a 3rd-person possessive suffix.

Could I just use the word (constantly) instead of this grammar structure?