The first one only got to genus and the second one got to species, however, was not assinged to any species.
Is there a way to know which species it is ? And if not it is ok to show my data this way (consider the last one as a specie)?
So no there is not really a way to see which species it is — it is in the reference database but the species label is unknown (probably because multiple species are too similar to differentiate with that marker).
Yes — 95% of the time these seem to be non-target DNA but I would confirm by grabbing a few of these sequences and seeing what they hit in NCBI-BLAST (exclude uncultured/unknown organisms from the search)