I don't know if you misunderstood what DJT has said, but this is an outright lie. DJT is not seceding any ground to Harris, plus he is doing the traditional thing of keeping a low profile during the Dem convention. The full on campaigning happens from Labor Day to the election.
I also don’t see any signs that he’s slowing down due to age. I’ve seen many in their late 70’s and early 80’s that are in good health and still cognitively sharp. Trump has a lot of energy for his age. I am also sure that security is now a big issue for the Trump campaign, especially since they have been told by the secret service that they can’t fully protect him at outdoor rallies anymore. Why risk it?
Many players in the US that have a bounty on his head unlike Kamala.
The voting officially begins in September in many states. Mail in ballots go out and will be in mail box’s no later than September 20th.