Learn English – Single word for the “estimated time of completion”

Time-consuming:

It was a time-consuming process, so he hired a professional to do it.

Closer to software:

Time-consuming operations should be run in separate background tasks.

Edit: Android calls them longer-running, meaning CPU-intensive and/or blocking:

A Service is an application component representing either an application's desire to perform a longer-running operation while not interacting with the user or to supply functionality for other applications to use. [...] if your service is going to do any CPU intensive (such as MP3 playback) or blocking (such as networking) operations, it should spawn its own thread in which to do that work.

I have no good answer for 'next night', but I commend to you 'yestreen' -- a word meaning 'yesterday's evening', which was still in (possibly affected) use in the 19th century. That may be Scottish; a more English version is 'yester-even'. See also 'forenight'. The first use of 'yestreen' noted in the OED was 1400 -- not necessarily Old English, but definitely unlike modern English.

Also, you may be pleased to know the existence of 'Saturnight', 'Sunnight', 'Tuesnight', 'Wednesnight', 'Thurseven' and 'Frinight'. In all cases, these referred to the night before the corresponding day. They are all labelled Old English -- so, earlier than 1400.

It might not copy perfectly, but here is the OED's earliest noted use of 'Thurseven':

Prose Charm: Against Elf-Sickness (Royal 12 D.xvii) in G. Storms Anglo-Saxon Magic (1948) 222 Gang on þunres æfen, þonne sunne on setle sie, þær þu wite elenan standan.

I can't help you with a translation.

A pleasing word meaning 'the end of the night, just before daybreak' is 'ughten', but the etymology isn't clear to me. It's in Beowulf (~1000AD) and fitted into the Germanic/Saxon/Old-English mishmash at the time.

Straying into invention, I suggest 'to-fall' -- a word meaning 'beginning of night', whose examples in the Oxford English Dictionary (which I've used for all the words listed) all look to the future. It was first used in 1425, though not in the meaning we're discussing.