In general, it is estimated that it takes approximately 600-750 class hours to reach a basic level of proficiency in Luxembourgish. This equates to approximately 2-3 years of consistent language study, assuming you are attending language classes for 3-4 hours per week.
However, it is important to keep in mind that language learning is a continuous process, and you may never fully reach "proficiency" in a language. There will always be more to learn and new skills to develop. That being said, there are certain benchmarks you can strive for to gauge your progress in learning Luxembourgish.
For example, the Common European Framework of Reference for Languages (CEFR) is a standardized system that describes language ability in six levels of proficiency, from beginner (A1) to proficient (C2). At the A1 level, you will be able to understand and use familiar everyday expressions and very basic phrases aimed at the satisfaction of needs of a concrete type. At the A2 level, you will be able to communicate in simple and routine tasks requiring a simple and direct exchange of information on familiar and routine matters. By the B1 level, you will have a sufficient command of the language to be able to deal with most situations likely to arise while traveling in an area where the language is spoken. At the B2 level, you will have a good command of the language and will be able to use it effectively for social, professional, and academic purposes. At the C1 level, you will have a highly advanced command of the language and will be able to understand a wide range of demanding, longer texts, and recognize implicit meaning. Finally, at the C2 level, you will have a mastery of the language and will be able to use it spontaneously, very fluently, and accurately without much apparent effort.
Again, it is important to keep in mind that these benchmarks are just estimates and will vary depending on your individual learning style and dedication to studying and practicing Luxembourgish. With consistent effort and the use of language learning resources, you can make steady progress towards fluency in Luxembourgish.