"I have finished this book."
Μετάφραση:Εγώ έχω τελειώσει αυτό το βιβλίο.
For me, this translation is acceptable. Very often Englih speakers drop the word reading, since it is unnecessary.
Then this is a spoken form.How wide is this used? Many othe words are often left out when speaking in English. E.g. You do this? As in Did you do this? Or 'you okay?' instead of' Are you ok'? Should these be accepted too? Furthermore words like ain't,gonna ,wanna etc are widely used when speaking. Should all these forms be accepted as correct as well?
I don't know what your native language is but as a Greek native I think the apparent reason for this translation is the typical (mistaken) way many Greeks speak English.They just replace Greek words with English ones.Such an example is also the phrase 'the food is going to finish' as in 'το φαγητό θα τελειώσει' you yourself commented in the past.
Another such a mistake I found is the phrase the 'lawyers have finished.' as in οι δικηγόροι τελείωσαν .This doesn't sound too correct to me.Finished what?
To sum up.All the phrases in English should be proof-read by an English-speaking native and explanations should be given when a spoken or less common form is used.
η μετάφραση είναι λάθος.Το ρήμα finish πρέπει να ακολουθείται από κάτι π.χ. I have finished reading this book.
Glossesweb, I can assure you the phrase is not only acceptable in oral but also in written English, the reason being that the word reading is implied. The other examples you quote are quite different, eg. you cannot say " How wide is this used", the phrase is "How widely ...." You do this, would not be said by an English speaker, unless of course it was a command, neither would wanna or gonna be used by an educated person. I think you can rely on Duolingo for an acceptable translation. As in all human endeavours some mistakes are made, but don't worry we native English speakers love to point them out to the very hard-working and in many cases voluntary members of the Duolingo team. Frankly I am in awe of their work, it is very far from easy to build a site such as this. I am an English native speaker, who has spent many years in the UK, U.S.A and Canada.
'how wide' I used this form on purpose :) .This is a spoken form.
You do this? as a question .Auxiliary verb is left out.Also 'You Ok?' Maybe the you do this example is not good .But what about You seen her?
What about the other 'finished' examples?These are typical Greek mistakes.
The point I am trying to make is that the' I finished the book' was translated that way for the same reason they wrote the food is going to finish,The lawyers have finished.-thinking Greek- not because they had in mind the alternative form.This is obvious to me as a Greek native.
Sigh! There is no point in demanding that an English speaker proofread the phrases and then refuse to believe them. You cannot say or write " How wide is this used" wide is an adjective, widely is the adverb which is necessary in this sentence because an adjective qualifies a noun (How wide is the river) an adverb modifies a verb.
People speak like that all the time.This IS a spoken form.This is not a question of whether believing you- a native- or not.I believe you.This is a question of which forms should be accepted as correct.Only educated forms or these forms also that are widely used but not considered correct by the grammar book?And most important(ly) this is a question of an English-Greek pidgin spoken in Greece!
glossesweb, jeanprendiville is providing you with excellent answers. I believe the confusion you're experiencing is the difference between spoken and written English. For example, if you are a student writing a formal paper, or someone working in a business office, you would never -- and I do mean NEVER -- write gonna, wanna, coulda without sounding uneducated if not borderline illiterate.
I cannot begin to approach your question about English-Greek pidgin. If you and your friends enjoy speaking it, well... have fun!