You according to hadith should offer the qaza salah (obligatory salah performed not on said time). You should offer the fard part of these salah as soon as you remember that you forgot to perform the obligatory salah.
Ibn Abbas narrated that the Prophet (PBUH) said, “Jibril (AS) led me
in (in Salat) twice at the House (the Kaaba). So he prayed Zuhr the
first time when the shadow was similar to (the length of) the strap of
a sandal. Then he prayed Asr when everything was similar (to the
length of) its shadow. Then he prayed Maghrib when the sun had set and
the fasting person breaks fast. Then he prayed Isha when the twilight
had vanished. Then he prayed Fajr when fajr (the dawn) began, and when
eating is prohibited for the fasting person. The second time he prayed
Zuhr when the shadow of everything was similar to (the length of) it,
at the time of Asr the day before. Then he prayed Asr when the shadow
of everything was about twice as long as it. Then he prayed Maghrib at
the same time as he did the first time. Then he prayed Isha, the later
one, when a third of the night had gone. Then he prayed Subh (Fajr)
when the land glowed. Then Jibril (AS) turned towards me and said: O
Muhammad (PBUH)! These are the times of the Prophets before you, and
the time is what is between these two times.” (Hadith No. 1393, Book
of Salat, Sunan Abu Dawud, Vol. 1; Hadith No. 149, Chapters on Salat,
Jami’ At-Tirmidhi, Vol. 1).
Update; In response to your comment (what is qaza salah)
In certain circumstances one may be unable to perform one's prayer within the prescribed time period (waqt). In this case, the prayer must be performed as soon as one is able to do so or as soon as one remembers it. Several Ahadith narrate that Muhammad sallallahu alaihi wasalam stated that permissible reasons to perform Qada Salat are forgetfulness and accidentally sleeping through the prescribed time. However, knowingly sleeping through the prescribed time for Salat is deemed impermissible. but still you have to perform the qaza salah.
Update - In response to your other coment regarding nonpermissible times for Salah.
In this condition sun is above horizon and you can offer Salah
In this condition sun is still half below horizon, and you cannot offer Salah
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