There are two reasons for your refusal: 1. Your travel plan should be sloppy, making people feel that you haven't done your homework at all, or you just used a travel plan to cheat your visa. 2. Your funds are not enough to support your travel plan, that is, your bank deposit and income certificate are not enough to support your travel.
These two aspects can be solved. You can make good preparations for these two aspects at the time of your second visa, and then explain them to the visa officer.
How to prepare for these two aspects and how to make an appointment for an interview are too numerous to mention. You can consider searching the "European Tourism Forum", and the homepage has detailed German visa strategies.