A fiance visa grants you entry to the UK for a period of six months during which time you are required to marry your fiance in the UK.
Once you are married you can apply for a spouse visa from within the UK. The spouse visa enables you to work in the UK and will initially be granted for a period of 30 months.
More here
https://www.gov.uk/uk-family-visa
As you will be technically a student you might like to read this.
https://www.gov.uk/tier-4-general-visa