Learn English – Is “fresher” really a “proper” English word

The use of doubts to mean questions is, AFAIK, Indian and also Spanish and Portuguese. See here for an explanation.

As I said elsewhere, saying "tengo una duda" (I've got a doubt) when putting your hand up is a common way to make a question in class for kids in Spain. It makes me wonder why English views interaction in terms of answering questions whereas Spanish (and Portuguese) sees it in terms of clarifying doubts. :-)

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.