The door here means level. That is, there are seven levels of Hell which are located on top of each other and will be filled in phases.
The seven doors of Hell which Allah has instructed in the Holy Quran, ‘Surely Hell is the promised place for all of them, it has seven gates, for each gate there is a separate class’ [Surah Al-Hijr: 43-44]
When the disbelievers are brought to Hell, its doors will be opened, then they will enter it to abide therein forever.
Allah says (interpretation of the meaning): The disbelievers will be driven to Hell in droves, and when they come to it, its doors will be opened, and the keepers of Hell will say to them: Did not a Messenger come to you from among you? Recite and warn you about the meeting of this day? Then they will say it must have come. In fact, the punishment of the disbelievers has been fulfilled today '[Surah Jumar: 81]
Then Allaah will look at the disbelievers and say, ‘Enter the doors of Hell to abide therein forever. What a miserable abode for the arrogant. '[Surat az-Zumar: 72]
After casting the inmates of Hell into Hell, its doors will be closed in such a way that there will be no escape from it.
Allaah says (interpretation of the meaning): “And as for those who reject My Signs, they are the losers. They will be surrounded by a blazing fire '[Surah Balad: 19-20]
Allaah says (interpretation of the meaning): “Woe to everyone who slanders people from behind and in front of them, who accumulates money and counts it over and over again, thinking that his money will immortalize him, never, he will be thrown into Hutama, Do you know what Hutama is? It is the burning hutashan of Allah which will consume the heart, surely it will encompass them in the elongated pillars' [Surah Humajah: 1-9]
May Allah protect us and our family from from the hell, that a very good remembrance. And may Allah reward you in aboundance. Please don't forget to subscribe me thanks