I would try to prevent the Holocaust from happening.

I guess I would try to warn people that the tsunami was coming.

i would find the first guy that started smoking stuff and congratulate them for inventing fire

Well that first guy smoking stuff will have enough to deal with so probably something else.

Get rid of Ronald Reagan.

I'd invent the printing press during the classical era and watch what happens from there. I guess the folks at Carthage would also enjoy knowing about paper making, better wind-powered sails for ships and to be on the lookout for those "Romanes"

I prefer to rewind time with me along, be young again, that kind of time travel. Of course with my knowledge and memories of up to before my "time travel", be retained. I could only remember what I could any way. The future would surely not happen exactly as the same before. Live a new younger life, a seemingly fresh restart at an early point in my life.

I would get a bunch of party hats in RuneScape.

time to kick that fish back into the water where it belonged. Stay in your lane, ancient precursor animals.

I'd find the guy who became the first guy to smoke stuff after the original first guy got stopped.

I would try to match Genghis Khan up with a proper dad.

Changes could have so many repercussions even well meaning actions could make things worse. The safer bet would be to collect lost books and art.

That said, stopping the Lincoln assassination is tempting. I'd hope to change reconstruction to better wipe out the confederacy, prevent lost cause doctrine, and better integrate former slaves into full citizenship and society.

That first guy smoking stuff is gonna get rekt

Bring back Sodium batteries and how to make them as well as solar panel production. Probably to Nikola Tesla.

To be a bit more precise whatever the easiest to produce versions of each are not the best ones so they could actually be produced at the tech level at the time.

I'm sure they would still end up creating equivalents of oil Barons etc. but at least it would be based on a cleaner tech and more able to improve from there.

Nothing just incase.

Depends on time travel method and how would it affect reality (would it create a new timeline or replace the one we currently live in?).