Some expenses are tax-deductible (steuerlich absetzbar). Your taxable income does not include the money you spent on those things.
For example, if you earn €50,000 per year, and you have a €10,000 tax-deductible expense, your taxable income is €40,000. You only pay income tax on €40,000.
Health insurance, business expenses and some pension payments are tax-deductible. Tax software and tax advisors can help you file a tax declaration and declare your tax-deductible expenses.