First check where the stress is: одинОчество (loneliness), колИчество (quantity)
The stressed О and E are always articulated clearly. In other syllables they turn either into А/И respectively or into schwa - as a beginner you can stick to А/И (just don't exaggerate them too much), and it will sound ok.

Based on what I said "одинОчество" and "колИчество" can be pronounced as "адинОчиства" and "калИчиства" (it's a slightly simplified version).