first i have to say (that) my english is not perfect in any ways... so if there is something wrong.. please correct me..

i think the most difficult part in learning english for chinese speakers is the tense... in english.. tense is very very important and sometimes very confusing too..

as the example, "i was trying to add him" in grammer, it is correct.. means he "was" trying... in a way give people a feeling that he not only tired but tried many times in the past... if you said.. " i tried to add him" kind of hint that you tried ( maybe only once) and fail to do so...

also.. the difference between "i am going to" and " i will " in some case, both are the same... but "i am going to" give people a feeling that you will do it very soon or in other word, you will do it as soon as possible... however, "i will" usually give people a feeling that you will do it sometime in the future.... maybe in 5 years time... here is an example.. if you say... i am going to buy a computer... usually means you will get a computer very soon.. on the other hand, if you said you will get a computer.. there is no time flame.. you just state that you might get a computer in the future...

correct me if i made some mistakes, please.