Hi Natasha,
When we refer to someone who is down-to-earth, we mean that the person is easygoing, practical, holds realistic views about the world and does not live in an ivory tower. This is the definition you will find in most dictionaries; however, it can have a less complimentary meaning beyond its literal or primary meaning (connotation).
Example:
A: "Many of Steve's juniors have climbed the corporate ladder, but he seems to be stuck in a rut."
B: "Well, let's just say that he is down-to-earth."
Based on A's description, we can infer that B views Steve as being content with the status quo and not setting lofty goals for his career. So, it depends on how "down-to-earth" is used in writing or a conversation.
"I am asking because in Russian it means one who is interested only in material things, everyday life, has very practical dreams and aims, doesn't think of philosophical issues like why do we live and if the God exists or not and so on."
Personally, I would use the word "materialistic" or "realistic" to describe such a person.
I hope this helps you.