Greek: Εν ἀρχῇ ἐποίησεν ὁ Θεὸς τὸν οὐρανὸν καὶ τὴν γῆν.
Ἀρχῇ is in dative case and preceded by εν because it expresses when something happened (vidē 1542.e in [1]), so εν ἀρχῇ means in the beginning or in the origin and foreshadows the recountment of the event that happened in that time. ἐποίησεν is a verb which means made, produced, created, brought into existence, brought about, caused, et cētera and whose object is τὸν οὐρανὸν καὶ τὴν γῆν. Οὐρανὸν means heaven either as the firmament or as where gods dwell (cōnfer 1.67 in [2], 1.497 in [3], and 897 in [4]) and γῆν means earth defined as the exact opposite of heaven.
English: In the beginning God created the Heaven and the Earth.
This is a complicated sentence because in the beginning God created acts differently on the Heaven than on the Earth. It is stating that the Earth was created and that from that point of the text on we should take it as already existing (vidē Genesis 1:2) but it is not claiming the same for the Heaven as it is actually created later (vidē Genesis 1:6-8). Since both were produced in the beginning, this makes the beginning not a point but a length of time, probably all the Seven Days.
Because everything created comes from the Earth and it was the first thing, the beginning means the beginnig of the existance of things other than God. Since the passage of time and the instantiation of position only applies to created beings, for God is atemporal and aspatial, the beginning is also the beginning of time and space.