If I make this year‘s 45000$ and I have 4 kids how much money I have returned from tax

You did not tell us whether your income was W-2 income with tax withheld, or if you worked as an independent contractor who will be paying self-employment tax.   We do not know how old the children are--so we do not know if you can get the child tax credit for any of them.  We do not know if you paid someone to babysit while you worked.   We do not know if you are single or married.    We can tell you that the limit for getting earned income credit is three children.   Provide some  details here, or --- use the Tax Caster tool that you were provided a link to in order to get an idea of how much you might get back.