Struggling as a java developer

Folks,iam working as a java developer from past 3 year's but still i don't have a proper grasp in coding and when any task assigned, Beacuse i dont even understand the real project code and iam not good at logical thinking . Due to not completing task on time iam planning to ask release from project I dont want to leave ,but iam unable to complete my task too due to which iam feeling ashamed daily Please suggest me ur ideas.