welcome to our community!
There is a very useful website provided by the government of the UK that gives detailed information about how to get a residence permit by marrying a UK citizen. You can find it here:
You can click on the headlines to get a summary of the steps you and your girlfriend need to take in order to reach your goals.
I will list you some of the most important things you need to keep in mind here:
- the visa you need is called "family of a settled person" visa.
- in order to apply for it you have to be outside of the UK
- you will have to pay a fee (~1400 £)
- both of you have to be over 18
- you will have to prove that you have at least 18.600 £ per year
- if you are not in a relationship with your girlfriend for at least 2 years, you have to be engaged with her in order to apply for this visa --> then you will have to marry her within 6 months after arriving in the UK
- you will have to prove that your knowledge of the English language is A1 or higher (you need a certificate for that)
Please read through the information given on the website linked above carefully. The bullet points I wrote down are just a brief overview.
If you understood everything and gathered all the required documents and certificates, you can apply for the visa on this platform:
I hope this information is helpful for you. If any further questions occur, feel free ask the community!
I will also link @Marcel and @Steven (our great lawyers here on the platform) that might have some additional information for you concerning the legal aspects of your plan.