Betz:
I got a electric 12V cooler box from Aldi so is ok to use cooler all time in my car? If I switch off the car engine then cooler box will be continue running but will be affect on my car battery?
No, the coller box only take electricity when engine is running. When you switch it off, the cooler box switches automagically to the cosmic beams 
:? Shall i buy a special box - Adapter something to protect the battery?
Yeah, it might be a good option. I would suggest a box called “another battery”. Disclaimer: second battery won’t also run forever, but at least you’ll protect the first one 
On the more serious grounds: if you switch your cooler box overnight and hide it in boot or somewhere cold, it should keep the cold overnight.
Also I will buy a Sat Nav so can you tell me which one is best to coverage Poland map include shown many of polish tiny villages! 
From the ones you can easily buy in UK, Garmin has the best maps (or what I was told). But the best map for Poland is Polish automapa.
Also I have change the route plan, I will catch the ferry from Dover to Dunkerque and drive to Madgeburg for stay hotel overnight. Next day will drive to Åask(nr Lodz) to see our friends and stay their place for overnight then drive to Warsaw to see others friends for a long weekend, Afterward heading to Brodnica (nr Torun) to see my girlfriend’s family.
This is a good plan.
Stop in Las Vegas truckstop in Mostki for a good meal and remember that Warszawa is second worst congested city in Europe.
I am so looking forward it…won’t be long! 
Enjoy!
And please, one thing. Take the correction stickers if your car is British registered and use them. This might be not so important on Western European motorways, but most Polish roads are single carriageways and you’ll otherwise dazzling all oncoming drivers.
It’s a good advice also for your own comfort, as many of them will flash you with their main beam as they will be thinking that you forgot to dip your headlights. When no reaction, they will flash more, more and more and, finally, they will put their main beam on as well 