## 5 Conclusions and Further Search  
In this study, we employed a mixture random effects model along with pairwise comparisons to analyze the tonal challenges encountered by L1-dominant Polish speakers learning Mandarin (L2), particularly in the context of T1 and T2, relative to TM natives. Additionally, we utilized Python to visually represent these tonal variations through line plots, facilitating a clearer understanding of the differences in tonal domains between the two groups. Furthermore, practical pedagogical recommendations were provided based on our findings; for example, increased practice with 16 tonal combinations, particularly focusing on high-ending tones. Pairing with T3 and T4 to form disyllabic words can be beneficial, because T3 remains in the low-tone range, while T4 benefits from its similarity to the stress patterns in Polish. This approach may help stabilize T1 and T2 tones in disyllabic words. Despite the T1T1 combination showing the greatest deviation from native Mandarin Chinese, it is still recommended to start with T1T1 training as it may be more effective than starting with T2. Additionally, given the individual differences in learners' perceptual abilities, educators should adapt their teaching strategies flexibly to suit different learners. To sum up, this research serves to address previous gaps in the literature concerning the performance of L1-dominant Polish speakers learning Mandarin (L2) in disyllabic words, specifically focusing on the challenges associated with T1 and T2. Moreover, it offers tailored instructional strategies, suggesting the incorporation of low-ending T3 and T4 tones to complement the training regimen, thus enhancing the overall proficiency of L1-dominant Polish speakers learning Mandarin (L2). This study reveals several findings that align with or diverge from previous research. Most prior studies on Japanese, Korean, and German speakers have identified difficulties with disyllabic words, particularly with T2 or T3, and noted position sensitivity. In contrast, our results indicate significant differences in the high tonal register of T1 and T2 compared to TM speakers, with no position sensitivity. Specifically, T2 and T3 are often confused in the production of the first syllable, confirming that T2 is a common difficulty for L1-dominant Polish speakers learning Mandarin (L2). Given the increasing importance of disyllabic word pronunciation, future research should explore whether there is an interaction or a stronger connection between tone and syllable position. Although this paper primarily focuses on the tonal performance of L1-dominant Polish speakers learning Mandarin (L2) in disyllabic words, it is essential to consider that previous studies have emphasized monosyllabic tones due to the teaching progression from simple (monosyllabic) to complex (disyllabic) structures. This step-by-step approach in teaching--starting with monosyllabics before progressing to disyllables--is logical. However, prior research on L1-dominant Polish speakers learning Mandarin (L2) shows that T2 and T3 are challenging in monosyllabic contexts [7; 41], and T4 presents difficulties as well [40]. This raises questions about whether difficulties with monosyllabic tones automatically resolve or exacerbate when learning disyllabic tones. A future research goal could be to trace the learning trajectory from monosyllabic to disyllabic tone pronunciation and compare the tonal performance in both contexts. **Author Contributions:** Conceptualization, H.-W.L. and M.-N.C.; methodology, M.-N.C. and H.-W.L. ; software, H.-W.L. ; formal analysis, H.-W.L. ; investigation, C.C. ; writing\(-\)original draft preparation, M.-N.C. and H.-W.L. ; writing\(-\)review and editing, M.-N.C. and H.-W.L. ; visualization, H.-W.L. ; supervision, M.-N.C.; project administration, H.-W.L. and M.-N.C.; funding acquisition, M.-N.C. and H.-W.L. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding.