My landlord's dog is agressive towards me

Hello everyone! I have a huge problem... My landlord's boyfriend moved in with us for a while because he's doing some works at his house and he brought his german shepherd with him. The dog is 2 years old and when they are home and they say to him to calm down is totally fine and just curious towards me, the problem is when i'm alone. I can't go out of my room/enter the house because he starts barking and growling at me and I don't understand why!! My landlord told me it's because he can feel i'm afraid of him and because i hide my hands and he feels i'm hiding something, but truth is he starts barking just hearing me coming home from the stairs or when i wake up and he hears me moving in my room. I spent time with him when his owners are home giving him food and caressing him, when he barks i tried speaking to him calmly and gave him my hand to smell so he knows it's me and that i'm not a threat but nothing works. Thank good my room and the exit are close so i just walk ignoring him but it's literally Cersei Lannister walk of shame!!! Do you know why his behaviour change so much like this? What can i do?

I should probably point out because i read the rules that the way they trained him is completely wrong. When he barks at me and doesn't stop right away when they tell him to calm down they hit him, and sometimes they threat him with a leash even though i never saw them hitting him with it. Beside this the dog he's totally in love with them and go crazy when he hear them coming back home... I don't know if this could explain his behaviour.

PS: i'm a foreigner so i probably made some grammar mistake :eyeroll: