In 30 days learning German is really difficult, but not impossible to do. In 30 days we have 720 hours, you have to dedicate a maximum part of it towards German learning.
All languages have different sentence structures according to tense, question, or imperative types of information. You need to master them, learn to fake them until you make it.
There is a book which claimed to do the same as your question. The book is on Amazon, I have not used it, or gotten any money out of it. You can try it yourself if it is something which can be useful. It will bring you to the A2 level.
Sentence Structure: The first step would be to learn these common structures, how and where they are used. If you know this theoretically you will be able to communicate most of the topics. (1 hour)
Verb Conjugation: Sentence structures are incomplete without the correct verb conjugation. So you have to learn this with the appropriate personal pronouns. This will make your sentence grammatically correct. (1 hour)
Vocabulary: As now you know the sentence structure and right conjugation, you have to use it with different kinds of context, and to do so, you need words in your mind. Here you can learn the words as per the context like shopping, eating, etc. This is the standard practice in German learning. You have to do this every single day. (1 hour)
Listening → Speaking: Above points are your base, to use them while speaking German. As kids learn the language from their parents by listening, you also have to listen to the German language as much as you can, preferably the native tone. So you can reproduce it while speaking, and your pronunciations would be nearer to the native tone with a little bit of accent. So by listening you can improve your speaking as well. German TV shows, Radio, or movies whatever you can get access to and have fun with. (2 Hours)
Grammar: Grammar is the crucial part, but with the shortcut, we did learn the sentence structure, but still there will be some topics that would need extra attention. So here you have to go through the grammar topics, their use, and application to make your German error-free. (1 hour)
Writing: You have to start with letter writing, writing a long text about any topic, or graphics or chart from the newspaper every single day to find out your mistakes and relearn them again and again. So that you can improve your writing part as well. This will also help you to identify the mistakes you are doing so that you can remove them before day 31. (2 hours)
The above things you will do every single day, until 31st day. Even if you just follow the above plan for 8 hours per day, you will learn much German, but you have to be totally committed to the language, as it’s not that easy, as this plan of mine seems. It would be the most logical way to achieve this task, you have immersed yourself within the language to get the best result out of these 30 days. You still have 16 hours left for each day, where you can give some extra time for the topics where you are not so good. So daily evaluation and action on them would make this task possible.
Do let me know in the comment if you were successful in doing so.
All the best.