Can low self esteem cause for example to do bad work or not studying well or not trying to solve a math problem because of thinking that it is difficu?

Poor concentration: Find a therapist w/ whom you feel comfortable talking. Cognitive ; esp. Behavioral therapy may be particularly effective. Simply talking about how you feel, by itself, may take a long time to bring change. Doing something that gives you a different experience can be key. Acting yr way into feeling ; thinking differently can work better than trying to think or feel yr way to acting differently.

Avoidance=problems: If you anticipate failure/disappointment and your response is to avoid things or do them half-heartedly, this leads to a vicious cycle, because you are also depriving yourself of the opportunity to practice skills. This leads to lower self esteem, which leads to more avoidance, which leads lower self esteem, etc. Talk to a therapist before this pattern becomes a life-long impediment.