Trump and Obama are almost like polar opposites. Obama was an outstanding representative of his black race, while Trump is a pretty sad representative of his white race. The Obama family behaved itself impeccably in the White House. Obama presided over the government with even-tempered moderation and spoke eloquently. Trump has been tarnished by personal scandal and speaks more like a high-schooler than a college graduate.
One of the biggest Republican complaints about Obama is the creation of ObamaCare, but much of ObamaCare was drafted by Congress which had to haggle over how to make it work. If the crazies in the Democratic party had not been kept in control by Obama's moderation, it would have been much worse from a Republican viewpoint. The biggest general criticism of Obama's foreign policy was probably his failure to enforce the "red line" against the use of chemical weapons in Syria. I support Obama's decision to work with the Russians to remove chemical weapons from Syria, rather than blow Syria to smithereens. We could not have "won" the war in Syria, and getting Syria to dispose of almost all chemical weapons except for chlorine probably meant that there were many fewer deaths from chemical weapons than there would have been otherwise.
I think Obama's negotiation of the Iran nuclear deal, the JCPOA, was a significant accomplishment that reduced the risk of nuclear war in the Middle East. Trump was very foolish to abandon the agreement. He may try to get Iranian concession on non-nuclear issues, such as support for Hamas, but he should have left the nuclear deal in place and worked to expand limits on Iran's other activities.
On the anniversary of Charlottesville, the main Trump issue that I support is immigration and support for white people, including the non-crazies who participated in Charlottesville because they opposed removing the Confederate monuments. The protesters against removing the monuments should not have tried to look like Nazis, but those in favor of removing the monuments, who had already won on the main issue, should not have violently opposed the marchers. Charlottesville now has the reputation as a place where free speech is unconstitutionally opposed by violence.
Trump is right that immigration has significantly changed the United States for the worse, at least for the former white majority. I support his efforts to get immigration under control. I also support his efforts to deal with Putin on a friendly basis. Russia's economy may be weak, but its nuclear weapons arsenal is second only ours. On the other hand, I do not support his confrontations with our traditional friends in Canada and Western Europe. And I don't like his bull-in-a-china-shop style. He threatens and blusters, but then (thankfully) often backs down to a more reasonable position.
I don't blame him for opposing the Mueller investigation. The Russian collusion investigation was started to try to declare Trump's election illegitimate, and has now morphed into trying to create a basis to impeach him. It may not be a "witch hunt" but it is a virulent personal attack on him by Democrats led by the intelligencia, Jews, blacks and Hispanics. It is racist to a significant degree. Trump may have played the race card first, but the response has also been extremely racist, so that the current tension is due to ill will on both sides, not just Trump's.
Trump is amazing in that he does not let the violent attacks against him deter him. Apparently they affect him, but mainly by making him angry. Although Trump is a poor example of what would expect as a representative of the white (formerly) ruling class, no polite, gracious member of this class could or would withstand these withering attacks.
So far, the Democrats' case seems so weak that it seems to depend mainly on Don Junior's meeting with the Russian lawyer in Trump Tower. This is thin gruel for an impeachment, although impeachment is really a political act rather than a legal one. If the Democrats take over the House, and if Mueller comes up with enough other material to convince some Republicans in the Senate, impeachment is possible. I really don't want Pence to be President, but maybe if he just took on a caretaker role until the next election, the country could survive. Right now the 2020 election does not look pretty.