Stain removal suggestions needed

[Danbor]

I'm one of those people that learn best by trial and error. Giving up has never been something I'm good at. Been more than a few times over the years that giving up would have been the better option in hindsight. Not this case, but it has happened.
Of course, trial and error usually works better with helpful tips along the way. So my thanks to those helping me.
I'm getting closer, but I don't have a clue how to fix those trees though!