First and foremost, establish the strong network of public transport in the country
this is not a proper sentence, it became a fragment. it will be better if you write this way; "first and foremost solution is, establish a strong network of public transport in the country."
It is the responsibility of government, however, to move anywhere in the town, transport must be available at any time within twenty four hours.
This sentence is not clear. May be you tried to say, "government is responsible to make a twenty four hours transportation system so that people can access the public transport when ever they want." if so, then why did you use 'however' in the middle of the sentence. 'However' indicates a contradiction between 2 ideas or instead of 'but' we can use 'however'.
Government should educate people through media and advertisements. Media is becoming popular, nowadays, it must play vital role in the society to realize how to control pollution.
you should write how media can play a role
your essay does not contain any specific example to support your solutions. i think it will be better for you, if you focus on one solution and provide a specific example for that solution. Don't try to put the whole picture in your essay, it's not possible to write about all solutions with specific examples in just 30 minutes. it will be better if you give one solution with specific example in one para, then another reason with another example in the next para. My point is one para with one solution and a supporting example. So if it is a 3 para essay then there will be 3 solutions with 3 supporting examples. This will make your writing comfortable, coherent and easy to follow.
don't use number such as firstly secondly to mention your solutions. it's so cliche. Better if you use 'main solution' for 1st solution, then, 'another solution' for the second and last one or lastly for the 3rd or last solution (which you did in your last body para). hope i have made myself clear.
wish you all the best