Every language has it's specific difficulties as foreign, the French pronunciation, the Spanish speed, the Chinese ... well leave it. The English has the "easiest difficulty" among all: phrasal verbs, which are of moderate importance and can mostly be avoided.

No basic English is one of the simplest languages to learn as an adult. Perhaps it’s difficult to master.

English has simple conjugations. That makes it much easier to learn to speak intelligibly even for adults. Old English dropped many of the complicated word endings because it was used by Anglo-Saxons with Vikings and Normans.