If you are not sure about your left hand position, try this tip. It may help you.
Perhaps the two most uncomfortable things to do with the LH are The Bar and trills / ornaments with the 3rd and 4th finger.
I base my general position on the solution to these two problems.
Start with fingers 3 and 4 on the string the best you can do (knuckles more or less parallel to strings and tips coming down perpendicular to string. Fig.1), then place the bar as well as you can. Fig. 2.
Even if you cannot hold down the Bar very well, this will be a good position for you.
Many chords will take you away from this Position A, but you must return to it as often as the music allows.
I find this helps to stabilize the left hand and I hope it will help you.
Use the drawings as an example.