How do I solve a rubicks cube. Can you recommend me some solving methods?
The most popular method to solve a Rubik's cube is the Beginner's Method. This is a simple and straightforward technique which involves solving the cube one layer at a time.

More advanced methods include CFOP (Fridrich), Roux and ZZ, emphasizing complex, algorithmic approaches for fewer turns and improved speed.

I would recommend starting with the Beginner's Method and gradually moving to more advanced solutions as you become comfortable with solving the cube. You can find tutorials, videos, and step-by-step guides for these methods online.
How long does it take to learn the Beginner's Method, and will I be able to solve the cube everytime?
It's hard to estimate since learning is very much individual. But you are likely to be able to learn the beginner method in a week or less.
Yes, you will be able to solve the cube every time, - but it will take longer than it will with the more complicated methods.