It is easy to get to level five before going to the Mountain Pass which you shouldn't really be going near if you haven't finished Act 1.
I do the Underdark before the creche.
Look to your party - would you be better off swapping A for B for this fight?
Check your gear - could you upgrade any of it?
Check your inventory - what bombs, potions, scrolls, etc do you have?
Are there any areas you could do to get enough XP to go up a level before taking on the tougher fight?
Look at build guides - would a respec help?
Right-click and examine enemies to see if they are resistant or vulnerable to anything.
Watch YT vids on the fights you are having problems with.
