μπορείτε σας παρακαλώ να μου πείτε το νερό βράζει πάντα στους 100 βαθμούς και έπειτα ρυθμίζεται να μένει σταθερά ζεστό σε όσους βαθμούς θες ή μπορείς να το ρυθμίσεις να βράσει μέχρι τους 40??

the water always boil at 100ºC, in accordance with the physics laws, no matter what you set on the kettle ))
but re your question, the kettle doesn't boil water necessarily every time you switch it on, but it just heats it up to the temperature which was set up on the switch.
So, if you want to boil the water first, you need to set up temperature to the maximum, wait until it boils it, and then let it get cool. You can also set up 'keep warm' button to a certain temperature and the kettle will automatically keep the temperature within this level (particularly, if you prefer to first boil the water, it will first boil it, then let the water getting cooler from 100 ºC to the temperature you set up, and then start switching on and off periodically, to keep the water at the desired temperature range