The tuition fees you pay will depend on where you are from. If you are from an EU/EEA country, you are able to attend Danish universities for free. If you are from any other country, you will pay tuition fees. Fees are different at each institution, as well as what level you are studying at. On average, you should expect to pay between DKK 45,000 and DKK 120,000 per year (3 - 8 million Naira per year). There are scholarships available for students, and these are offered by individual institutions, as well as other initiatives.
Your living costs will depend on where you choose to live, as bigger cities will be more expensive than smaller cities and towns. On average, you should budget for between DKK 6,000 and DKK 13,500 per month (396k to 890k Naira per month).