first time сначала

With sea water, bromine must first be concentrated before the steaming-out process becomes economically practical.

The lateral stress decreases initially with time until...

At first, these results should be surprising, but a closer look shows that...

First we consider fundamental modes and then high-order modes.

пе́рвое января́ [февраля́] — the first of January [February]; January [February] the first

уже́ пе́рвый час — it is past twelve

в пе́рвом часу́ — past / after twelve

полови́на пе́рвого — half past twelve

три че́тверти пе́рвого — a quarter to one

страни́ца [глава́] пе́рвая — page [chapter] one

пе́рвый но́мер — number one

пе́рвый эта́ж — ground floor

пе́рвая по́мощь — first aid

пе́рвые плоды́ — first fruits, firstlings

он пе́рвый заме́тил [сказа́л; ушёл] — he was the first to notice [say; go]

пе́рвый учени́к — best pupil

быть / идти́ пе́рвым — lead, take the lead, excel

пе́рвый шаг тру́ден — ≈ it is the first step that counts, everything is difficult before it is easy

пе́рвая скри́пка — first fiddle

игра́ть пе́рвую скри́пку — play first fiddle

пе́рвым де́лом — first of all

в пе́рвую го́лову / о́чередь — in the first place; first and foremost

из пе́рвых рук — first-hand; at first hand

информа́ция из пе́рвых рук — first-hand information

на пе́рвый взгляд — at first sight; on the face of it

не пе́рвой све́жести — not quite fresh, stale

Пе́рвое апре́ля — April first, April's Fools' Day, All Fools' Day

при пе́рвой возмо́жности — at one's earliest convenience; as soon as possible

с пе́рвого взгля́да — at first sight

с пе́рвого ра́за — the (very) first time; right away

On the far side of the Moon a similar powder will remain fixed at the place where it originally (or initially) fell upon the surface.

Chemists originally believed that...

At first (or In the beginning, or Initially) the machine operated trouble free.

At the outset (or From the start) it seemed possible that...

The plant will operate at lower power to start (or begin) with.

Early in the game we built a sled on which we mounted the exposure chamber.