what are russia and ukraine fighting for?

Russia is not engaged in military combat with Ukraine. The Ukraine government of Kiev is attacking the Russian speaking Ukrainians in the east and south because they protested, dissented and occupied local government buildings. Kiev wont negotiate with those residents in the east who want to vote for independence or autonomy. Not all people in the east are pro-Russian, they are Ukrainian citizens.

Russia is not fighting. It's Ukraine or more exactly the US backed govt that is fighting its own people. Or that is exterminating its own people with cluster bombs, tanks, military aircraft and MLRSs.

The US wanted to have a puppet govt in Kiev and orchestrated an unrest and a coup last winter. When eastern Ukraine didn't accept the coup and started protesting, the US required the newly set Ukrainian govt to crush the rebellion. And the Ukrainian coupist govt started exterminating eastern Ukrainians instead of talks.

Some Ukrainian MPs required the coupist Ukrainian govt to stop this extermination and proceed to talks but some of these MPs were accused of political offenses and a wirt was issued against them. They are Tsarov Oleg, Simonenko to name a few.

In February, this coupist govt was raised to power by Ukrainian neo Nazis (when asked by Rohrabacher, Nuland had to confess) and now eastern Ukrainians are fighting neo Nazis. The US and EU are helping the Ukrainian neo Nazis and Russia is helping fight neo Nazis.

Oil, shale gas? Remind me whose son was appointed to the board of directors of Burisma Holdings. So, it's the US officials who are fueling fighting in Ukraine.

Do you want in language? OK, here you are.

The US wanted a puppet govt but the previous Ukrainian president Yanukovich was not a puppet enough. Then, the US spent more than $5b to destabilize Ukraine and succeeded in some way. After Yanukovich signed an agreement with opposition leaders under supervision of the EU the opposition was encouraged (by someone, guess who?) to oust the president instead of fulfulling the agreement. Eastern Ukraine didn't accept this ouster. Then, the coupist govt sent their envoys to oust local authorities. Those envoys were welcomed in western (more Nazi) Ukraine and given a hostile reception in eastern Ukraine (and Crimea).

Then, instead of talking to protesters in eastern Ukraine and Crimea, the coupist govt tried to suppress them by arresting more active protesters and threating to kill and killing some others.

Crimea said no to Kiev and was lucky to shut its door and leave Ukraine locked outside. But eastern Ukraine was less lucky and now is suffering from the current punitive operation by the US backed govt.

All the rest of the "issues" are just window dressing.

Also for a window by the sea. There was in the old USSR, a Russian navel base in the Crimea

I believe, Putin wants the old USSR back as buffer from the EU and the West in general.

Besides losing land (territory ) in the USSR break-up, the Russian government lost much tax revenue .

Ukraine has massive oil reserves. Putin and his cronies in Russia want to steal the oil. Ukraine has a large ethnic Russian population and Putin is manipulating them to start a civil war and create an excuse for Russia to move in and take over (read: take the oil).

All the rest of the "issues" are just window dressing.