why (for example) Bulgaria didn't get such rich donations?
If by "rich donations" you mean EU budget transfers, cohesion funds, structural funds, and related support received as EU members, then
Bulgaria has received more EU funding per capita than Poland. Poland has about 38 million people, Bulgaria has about 6-7 million population, so even though we got more money overall, per capita Bulgaria received more. Slovakia, Hungary and Romania also received more money per capita than Poland.
If you give three guys 1000 bucks, and then you give 10 guys 1500 bucks, then you gave the 10 guys more but the three guys are generally happier with your gift. :)
Why is Bulgaria in such an abysmal state economically compared to Poland, despite receiving more money per capita? We are a Latin civilisation country, Bulgaria is Byzantine - they will always steal considerably more than us. Theft is inherent in Byzantine and Turanian civilisations.