You can't beat 2-3 ennemies at once, it's pretty risky, even at a high level, even if you're a Soul's Games Master.
Try to Lock on one of them, approach him quietly and make him come to you alone, kill him and then do it again with another one. Or use a stone to throw it at him and make him come to you.
Look for shortcuts, Bloodborne is full of them, so you don't have to walk again all over the city to return to the Boss.
Then, use your blood echoes for three things : Heatlth, stamina and strength. Boost them all the way you can, and don't forget to upgrade your weapons, this is very important too.
For Clerical Beast, use the Molotov Cocktail, the Bastard fears fire. Try to shoot him with your Pistol at the head too, this will cause him to fall down, then do a visceral attack. Also the Boss hits you A LOT with his left arm, so to avoid being touched, stay close to his right arm, dodge then attack 2-3 times and fall back.
In this game you have to be patient : 1-2-3 attacks and then fall back to wait for another opening.
You can also stand far from him, he will jump at you, dodge this attack (it's quiet easy), then attack him.
Don't get discouraged, the start is the most difficult part of the game because you don't know where to go, what to do, the ennemies are a lot and you're weak.
If you lose to the Boss, run to him, you can dodge EVERY ennemy in the game by running/sprinting, don't waste time killing a second time all the beasts.
Good luck !
If you have any question, don't hesitate.