What kind of topic can I use for my dissertation? It should be marketing related and should also contain student life and way of living.

Have you had any experience working or studying with international students at your University? One possibility would be to do a case study on how to attract a specific group or type of international student to your University. Apart from being an interesting study, it could be of real value to your University (and others) should you be interested in making a career in this field afterwards. You may even find you receive a lot of support from academics, staff and students if you were to do your research in this area.

By choosing your own University, it should be easy enough to find out what its competitive strengths and weaknesses are in relation to other Universities within the higher education sector in your part of the world. From there, you could begin to put together a business development plan including a marketing strategy. A marketing plan would naturally include what student life and ways of living are like in your University and how to make it more appealing than other universities, as part of an overall strategy to attract international students (possibly at a miminum level of academic achievement, in a specific area of study, or program) to your University.

Questions could include:

What is the overall size, characteristics and trends of the international student market internationally, within your country, and area you live?
What criteria do international students use when when searching for a University?
How do they carry out their search?
Is student life and ways of living an important criteria in helping them (and their parents) make a decision?
What sort of academic programs, services, facilities or lifestyle factors would help sway a prospective student's choice?
Who is the decision maker?
and so on.

Whatever topic you choose for your dissertation, I wish you luck :)