Being rejected is normal, maybe you are to slow I am in no position to judge, but maybe they just didn't understand what a junior without 5 years of practical experience is. Even a senior can slow down by lacking domain knowledge or missing knowledge of a particular framework.
you are a beginner don't let others tell you how they perceive your efficiency. Move on learn the best practices, challenge yourself and grow .... besides that no one looks at the failures before your success but giving up will never let you reach success ...
j
stuff ;)