Different students can have different difficulties and problems in learning English. They can make different mistakes in English pronunciation, grammar, orthography and vocabulary usage.There is a connection between the native language of a learner and particular difficulties in learning and using English and the kind of mistakes a learner typically makes in English pronunciation, grammar and vocabulary as there is native language interference in learning and using English.Listening comprehension and speaking in English are the skills generally more frequently used than reading and writing in daily living in an English speaking country. Listening comprehension and speaking in English are more difficult and more important for learners to master than reading and writing. When reading and writing a text a learner has more time for thinking and pauses than when listening and speaking in English in daily living.A learner can also look up unknown vocabulary in English dictionaries and use other English reference books when reading and writing a text in English which is impossible when listening and speaking in English. Therefore listening comprehension and speaking in English are more difficult than reading and writing.English vocabulary for daily living requires more time and is more difficult to master by foreign learners than English grammar. One of my articles in this forum describes difficulties in learning English vocabulary.I highly recommend that learners read the reference book titled Practical English Usage by Michael Swan to reduce making mistakes in English.