Personal finances are not intuitive for everyone, and it can be a challenge to know what to do when you haven't been taught. Congratulations on recognizing that you need to make a change.
The first step that I would recommend is what you've already done: Assemble your bank statements so you can get an accurate picture of what money you currently have. Keep organized folders so you can find your bank statements when you need them.
In addition to the bank statements for your checking and savings accounts, you also need to assess any debt that you have. Have you taken out any loans that need to be paid back? Do you have any credit card debt? Make a list of all your debts, and make sure that you have folders for these statements as well.
Hopefully, you don't have any debts. But if you are like most people, you owe money to someone, and you may even owe more money than you currently have in your bank accounts. If you have debts, fixing this problem will be one of your goals.
No matter what your debt is, you need to make sure that from now on, you don't spend more money than you take in as income. To do this, you need to make a budget.
A budget is a plan for spending your money. To get started with a budget, make a list of all the income you will receive this month. Add it up, and write that amount at the top of a page. Next, you want to make a list of all the expenses you will have this month. Some of these expenses are more or less fixed: rent, utility bills, etc. Write those down first. Some of the expenses you have more control over, such as food and entertainment. Give yourself some money to spend on each of these. You may also have some larger expenses that will happen in the future, such as a tuition or insurance payment. Allocate some money to those, so that by the time that payment comes around, you will have saved enough to pay for those expenses.
If you find that you don't have enough income to cover all of your expenses in a month, you need to either reduce your expenses somewhere or increase your income until your budget is at a point where you have money left over at the end of each month.
After you've gotten to this point, the next step is figuring out what to do with that extra money left over. This is where your goals come into play. If you have debt, I recommend that one of your first goals is to eliminate that debt as fast as possible. If you have no money saved, you should make one of your goals saving some money as an emergency fund. See the question Oversimplify it for me: the correct order of investing for some ideas on what order you should place your goals.
Doing the budget and tracking all of your spending on paper is possible, but many people find that using the right software to help you do this is much easier. I have written before on choosing budgeting software. All of the budgeting software packages I mentioned in that post are from the U.S., but many of them can successfully be used in Europe. YNAB, the program I use, even has an unofficial German users community that you might find useful.
One of the things that budgeting software will help you with is the process of reconciling your bank statements. This is where you go through the bank statement each month and compare it to your own record of spending transactions in your budget. If there are any transactions that appear in the statement that you don't have recorded, you need to figure out why. Either it is an expense that you forgot to record, or it is a charge that you did not make. Record it if it is legitimate, or dispute the expense if it is fraudulent.
For more information, look around at some of the questions tagged budget. I also recommend the book The Total Money Makeover by Dave Ramsey, which will provide more help in making a budget and getting out of debt.