This text is missing some spaces, please add them: Theyachievedthis,butonlyafterquiteaneffortforFelixhadhisheartsetontheidea,andafterthisheturnedtowardsmathematicsasthesubjecttostudyatuniversity.
They achieved this, but only after quite an effort for Felix had his heart set on the idea, and after this he turned towards mathematics as the subject to study at university.