关于“下定决心学英语”的英文翻译，综合多个来源的信息，以下是准确且自然的表达方式：
核心表达结构
- 使用现在完成时态：
*I have made a firm resolution to master English.*
*He has made up his mind to learn English well.*
- 使用固定短语：
*I have decided to master English.*
*He has decided to learn English well.*
扩展表达建议
- 强调坚定性：
*I have made a firm resolutionto master English.*
- 添加行动承诺：
*I am determined to practice English every day.*
- 结合目标说明：
*I have set my mind to achieve a B2 level by 2025.*
常见错误避免
- 避免时态混乱：
*He makes up his mind to learn English well.*（应使用现在完成时）
- 短语搭配错误：
*He made up his mind to learn his English well.*（应去掉定冠词"his"）
通过以上结构，可以清晰表达“下定决心学英语”的决心与行动方向。