For a good book on how to play with a plectrum try Plectrum Technique by Stuart Clayton. (bass line publishing). It’s content is full progressive plectrum exercises which are very helpful.
As others have mentioned, the key to learning is patience, always practice etudes slowly. Have a consistent structured practice routine & learn to keep emotions, like frustration,,out of the process. Think what you can achieve over the long term not by next week. It’s all in the mind, learning is a mental thing. Most importantly find a GOOD teacher.