Which they had 8 years to prepare for. Congressional Republicans and Donald Trump are incompetent. Repealing and replacing Obama care was their number one priority and political mantra for the entire Obama administration, and they bungled it. They couldn't agree among themselves yet they had years to work on it. Career conman Donald Trump couldn't negotiate a deal despite literally writing the book on negotiating deals.
The one thing Trump was definitely supposed to be good at he failed spectacularly. The only consolation Trump-lovers like yourself could possibly have is that Trump didn't actually do any negotiating. Despite supporters and aides touting his negotiating ability throughout this whole process, and Trump himself promising the best deal imaginable, it's more likely the Trump spent the whole time (and most of his presidency) golfing. So the only way you can excuse Trump's so far disastrous presidency without admitting that Trump is a gigantic incompetent and fooled you saps into believing he wasn't is that maybe you can say he hasn't actually done any work yet.
Maybe Trump really is an effective administrator and you'll start to see him really get to work when he gets back from his 2 month vacation. Currently the United States doesn't have a president. It has a retired golfer charging taxpayers for his golf trips.