Can’t you download offline maps for the whole country?
On my phone I have two sets of offline maps for my + neighbor countries. Microsoft is free, Garmin was one time purchase. Both work OK without Internet.
Honestly, the way Google changes the goal posts and rearranges the furniture within its own apps, I stay well clear of that mess when I need consistency and reliability. My phone remains a phone when I'm driving and need an uninterrupted, non-internet, non-phone navigation device.
Downloading the data at a level of detail required for my needs would be many GB.
Technically that’s indeed many GB, practically modern phones have many more GB available, e.g. my one has 32GB flash memory.