Is it permissible for a person who does not pray and frequently utters blasphemy to perform Umrah, and what should be done to achieve a positive outcome?

Neglecting prayer is among the greatest sins, and one who abandons it out of laziness may even exit the fold of Islam. It is obligatory to promptly establish prayer and maintain it. If you are committing acts that necessitate expiation, hasten to repent from them. Merely performing 'Umrah (definition) does not necessarily lead to a change in your condition, but hastening to repent and being sincere in it may lead to uprightness.