Piotr,
Firstly welcome to Ribnet and to boating. Congratulations on getting your first boat. I'm guessing from your questions that you're pretty new to all this - that's no problem - everyone on here was a newby once.
I'd recommend in the strongest terms to find a local sea-school and sign up for your RYA Level 2 powerboat certificate. It will focus on boats a bit larger than yours but will introduce you to all aspects of safety, navigation, boat handling, launching & recovery, plus what to do when it goes wrong and what kit you should have.
As well as building a firm foundation to keep you and your family safe, it'll be a fun and educational 2 days! Try and find somewhere that will give you some time in small tiller-steered boats like yours.
Course link, plus list of locations is here
https://www.rya.org.uk/training/cour...-handling-pl2c
