Donations to charity are a Schedule A Itemized Deduction and will not reduce any self employment tax on a schedule C Net Profit. Schedule A Itemized Deductions or the Standard Deduction (whichever is more) will reduce your total taxable income so you might owe less regular income tax.
For 2019 the standard deduction amounts are:
Single 12,200 + 1,650 for 65 and over or blind
HOH 18,350 + 1,650 for 65 and over or blind
Joint 24,400+ 1,300 for each 65 and over or blind
Married filing Separate 12,200 + 1,300 for 65 and over or blind