(here why do you want to change merits into advantages? any information?
that is word choice, i think using advantages and disadvantages are more suitable than your words.
On the one hand, a mobile phones poses have some negative effects for on its their users in several two aspects.
(why do you want to change this sentence, gramatically wrong ?)
of course, you can use a mobile phone,
i know the structure have effect(s) on st, so i think your sentence should be changed
i replace several ...two, because i see there are two supporting ideas in that paragraph,
Nowadays, we can / or it is easy to make a phone call with our friends almost anywhere, such as in the subway, the countryside or even another countryies.
(here is "another country", so i think it's better no plurual form)
i think it should be another countries, of course, that is just my idea, hihi
Likewise moreover, we can also text send messages with beautiful photos or even high-quality video clips to share the exciting moment of in our life.
(here it's just another example to support the subthesis, so i htink likewise/similarly is better than a word of progression)
moreover is not a word of progression, it has meaning the same as in addition, to list another example
Apart from that Besides, a mobile phone has also become an important entertainment equipment.
(here you cannot add a before euipment, because equipemnt is uncountable noun)
yes, i made mistake here, thank you.