If the "how long will it take me" refers to the time to build a strip built kayak, the answer is, somewhere between 200 and 300 hours.

If you plan to use it on the open ocean, you will need bulkheads and hatches, so it might be closer to 300 than 200.

There are a lot of good designs available as pictures, plans or kits.
While a lot of people here will be prepared to offer useful advice about designs, there is a lot to be said for doing some research yourself and looking at the many websites available.

One of the problems with recommending designs to someone is that there are so many variables to consider; things like your experience, fitness, balance, intended use and so on.

Asking the questions you have asked here is a good start, but you will still need to do a lot of research to understand how appropriate the replies are to your particular needs and capabilities.

My initial thought is that for someone your size, something between 4.5 and 5.4 metres long and with a beam around 52cm to 58cm would be a good start. However there are quite a few assumptions built into that recommendation.