Buying from Lenovo in any country requires a buyer IN that country, with an address IN that country, and with a credit card issued IN that country.
E.g. you can not buy a Thinkpad from Lenovo USA, pay with a Turkish credit card and have it shipped out of the country.
For that you need a US resident with US address and US credit card, who is also willing to ship it on to Turkey/Greece.
Where you buy a Thinkpad from is less relevant, because it is possible on every machine to replace the keyboard.
The specific things to look for (also in a used one) are: no BIOS password, CPU/GPU/RAM (because nowadays they are mostly soldered), good batteries, and less urgent: LCD (should be at least IPS).
On most laptops you can swap LCD relatively easy, so if you find one with a low(er) resolution or cracked screen, but the rest is good, go for it.
On some you can still add RAM, which is cheaper to buy than from Lenovo, so don't stare yourself blind on that.
HDD/SSD, wifi, WWAN and charger can be bought separately and also usually cheaper than from Lenovo.
Have a look at the shops that advertise at the top of their webpage:
https://thinkpad-forum.de/
They would probably ship (duty/tax free) to anywhere in the EU, and maybe also to Turkey.
Finally, buying last years model, such as T480, will be a lot cheaper than the latest/current models.