Time Traveling teacher?

Chapter 1

A strange figure, cloaked in shadows, approached an equally strange, humongous castle. To him, it wasn't just a mysterious castle, it was home. The place he had spent the majority of his teenage years. He knew that the feast would be underway and he should enter the castle, and yet he lingered. He took in the immense castle's beauty and grandeur. As he did this, his mind brought him back to the events that for him, occurred moments previous, but for others, occurred 25 years in the future.

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Harry Potter had received a very strange request. He had been asked to come to Headmistress McGonagall's office. Normally, that wouldn't be strange, but given that he had graduated Hogwarts, and it was still summer, he found the request quite odd. Nevertheless, he went anyway, because surely McGonagall had a reason for summoning him.
He prepared to leave home, said goodbye to his wife Ginny and stepped into the fireplace.
He yelled,
"Headmistress McGonagall's office at Hogwarts!" As loud as he could, and within seconds, he was there. Although, the Headmistress didn't seem to be.
He looked around in confusion until he spotted a note on her desk. Seeing that it was addressed to him, he began to read. The note said,
Dear Mr. Potter,
I know you must think it strange for me to call you here on a summer afternoon, however. It was not I who wanted to speak to you. Prof. Dumbledore's portrait happened to be the one who requested your presence, but as he is not a real person, he asked me to summon you instead. I don't know of what he wishes to speak with you but I wish you luck. Death has not changed Dumbledore whatsoever.
Best wishes,
Headmistress McGonagall

After reading the note, Harry quickly located the portrait of Albus Dumbledore. Said portrait appeared to be sleeping, but Harry knew better, he called out Dumbledore's name to alert him of his presence.
Already, Harry was suspicious. Dumbledore had his trademark mischievous twinkle in his eye. One that Harry knew would bring nothing but trouble. Harry was snapped out of his musings by his former professor's voice.
"Harry my boy, what brings you here?" Dumbledore asked
"Don't play dumb with me, you know why I'm here, I however, do not."
"Alright, I called you here for a reason. Before my death I discovered some rare and ancient magic that has to do with time. It can send a person back in time for a certain period of time, if that makes sense. I waited to reveal this to you because I thought you still needed to mature somewhat, and now you have.
   If you wish, I can send you back in time to meet your parents when they were 17. You are very powerful and could fill in as the Defense Against the Dark Arts teacher, as I recall not having one at the time. Should you accept, we can begin now." The portrait explained
Harry thought for a moment, "I–I accept."

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Harry snapped out of his memories of what brought him to this place and decided to head inside, at least he could make an entrance, and he had the perfect idea...
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After a long train ride and what seemed like an even longer day, the marauders were sitting down tuning out Dumbledore's ramble at the Hogwarts start of term feast.
Once again, James Potter failed to ask out Lily Evans and was moping about it to his devilishly handsome, best friend, Sirius Black. Sirius consoled James while their friend Remus Lupin looked on. This continued for a few minutes when suddenly, the doors slammed open and there stood a cloaked person with his head down towards to ground.
  Dumbledore cautiously stood up, he could feel the power radiating off this young man.
"Who are you?" He asked. The man didn't respond at first so Dumbledore asked again. When he finally did respond he said these words,
"My name is Harry—Harry Potter."
This caused little bit of shock among the Marauders and their peers seeing as James had no siblings or relatives to his knowledge. Then the man lowered his hood and you could see that he could've been a twin to James.
"Hey prongs, you know him?" Remus asked, using James' nickname
"Nope, maybe he's a distant relative?" James replied, still perplexed.
At the point the still mysterious man called Harry spoke again.
"Seeing as you have no one, I would like to apply for the defense against the dark arts position."
"How do I know your qualified, you must be 20,21" asked dumbledore
"21, how about we duel? I'm sure I can prove to you first hand how qualified I am" Said Harry.
"Alright then" An apprehensive Dumbledore replied
This caused whispers among the students, no one had ever dared to duel Dumbledore, not since Grindelwald.
Harry then created a large, protective dome around them so the students wouldn't get hurt by any spells gone awry. Spells like Expelliarmus, Confundus, Stupefy and many others rang around the hall until by the work of a miracle Dumbldore was disarmed, causing all the students and faculty to collectively gasp.
"It seems I was wrong about you Mister Potter, you are qualified and the job is yours to take, but one more question."
"Thank you." he said
"Do you have any relation to our young James Potter over here?" Dumbledore asked out of curiosity
Harry hesitated before reasoning with a curt "No"
"Alright then, Professor Potter welcome to Hogwarts.

Authors Note:
Ok I have Hardly any ideas so this story might go up for adoption and also I know this chapters really short
Disclaimer:
I don't own anything all rights and characters go to J.K Rowling
-Belle_G34

EDIT:
I decided to add some serious changes to this chapter. I lengthened it by about 700 words and did some editing, so I hope you guys enjoy it.