This paper discusses the impact of L2 learning experiences on L3 learning. Students who have previous knowledge of English (second language, L2) and study German as a major (third language, L3) were main research subjects. The study primarily explores the difficulties and main problems of L3 learning and whether the L2 skills are perceived more as help or as interference. Furthermore, the correlation between the L2 language level and the L3 learning effect is considered. The results show that L3 listening and oral communication are considered particularly difficult for most learners. The L2 and L3 language levels correlate positively with each other. In addition, L3 learners with an advanced L2 language level can apply L2 as tool in L3 learning better than those with a medium L2 language level. This finding is consistent with our hypothesis that L2 learning experiences have a positive impact on L3 learning.