Four days before their Euro opener against Scotland on June 14 in Munich, Fullkrug said he was at ease with Germany coach Julian Nagelsmann's decision to name Kai Havertz as the starting striker for the hosts.
"It is important to be honest and return that honesty in such talks," he said of discussions he had with the coach. "So I gave my opinion.
"The coach has the power and takes the decisions and that's the right way. Since we were young footballers we were taught about competition," Fullkrug told a press conference.
"We have this competition thinking and you have to remember that constantly. It is all for a big and special thing. We are all ambitious to play as much as possible and carry responsibility.
"Kai has my full support and I wish him all the goals possible because that will take us forward in this unique chance we have," said Fullkrug.
The Borussia Dortmund striker is a late international bloomer, having been a surprise addition to the 2022 World Cup squad where he was one of only a few players to escape scathing criticism following a first-round elimination.
"We are going into the tournament with a good feeling and you have to identify with your role and still accept it and see it as motivation to work in order to go beyond just this role and get more playing time," Fullkrug said.
The forward is the only out-and-out striker in the squad, with Havertz a more versatile attacker and not a natural centre forward.
"Basically it is good to have two different types of strikers. Kai is a completely different striker, defined by a different game. We are both very confident. I don't think many teams will be happy to play against us."
Hosts Germany, who also face Hungary and Switzerland in Group A, snatched an 89th-minute 2-1 comeback win over Greece last week in their final warm-up, failing to impress.
"We were a bit lethargic (in the first half), which made me wonder a bit. That will certainly not happen in this opening match," said Fullkrug.
"There will be times when they (Scotland) will be defending further back. Hopefully it will depend on our performance and not the opponents'. We have to have a certain arrogance. We have the quality in the squad and it is part of a team that wants to go far in the tournament."