Is it true that President Trump donates his salary from being president? $400,000 per year?

Donating is not paying taxes.  And the amount of tax is not the amount deducted.  That is not how tax deductions work.

sure...........................

Yes, he does.  He is the first.  He spends very little on his golf trips also because other presidents have spent a lot more on golf and travelling the world.  President Trump came to a decision in his life to start paying back.  America has been good to a lot of us and it is time to pay back.  America is struggling because of poor leadership by both democrats and republicans in the past.  Bad wars and very bad trade agreements.  The worst was Obama's Iran money.  President Trump saw his great nation going down and he made a decision to do something about it, even if it cost him greatly.  And it has.  He is the most hated President ever, but he has stepped on toes that needed to be stepped on for many, many years.  And the American people LOVE HIM for it.  He has only our interest in mind and he is a Great President.  He will go down in history as the President that kept America from destruction.  Restoring Judeo-Christian values alone will benefit this nation more than anything.  She's had traitors, she's been betrayed and she's let degenerates breed and divide, but God willing America will be Great once again.

look over there>>>> while his privately owned businesses collect millions from taxpayers.

Yes it is true that he donates his salary. Yes it is true that it is tax deductible. No, it does not mean he pays $400,000 in taxes. Donated money simply offsets income. So the taxes he pays would be based on all other income he has other than his presidential pay since that amount is donated. We will see how that plays out when his creditors call...

Trump donates all but $1 of his annual salary. He's not the first president to donate virtually his entire salary. Obama didn't donate his entire salary, but a sizeable portion. He also donated his reward for winning the Nobel prize. George w before him also donated a sizable portion of his salary to charity. 

It is deducted from his taxable income, not from his taxes. Why don't you know that?

That's not how donations work. A donation of $400,000 might save you $150,000 in taxes, but that's still a lot more than the $750 in taxes Trump has been paying. Further, Trump keeps getting the American taxpayer to pay for his golf trips (3x as many as Obama) to his hotels and golf courses, so he's making a fortune off the US taxpayer. 

That would be true. But there is a rule about donations to government agencies being tax deductible when in government. Guess where the donations are going? 

Yes, Trump is donating his net salary to charity.  No, that's not the same as paying $400k in taxes.  The amount he donates is deductible from his other earned income.