Not only Chelsea, PSG actually already made an offer above €100 million. One of the media stated that PSG offered €130 million for Osimhen. But Napoli rejected the offer because they want to sell him at €150 million. Actually, Osimhen's market value is only around €100 million but Napoli seems to not selling him at low fees. Napoli may try to keep their main attackers for the next season (Osimhen and Kvaratskhelia). However, there are more and more rumors related to these players. The latest news I heard from Napoli that they are trying to keep one of those attackers at least.
So far, there have been no further negotiations with Osimhen. Previously, Napoli had lowered their starting price to £100m. They also actually still want Lukaku to be at their club from Chelsea, with the option of Osimhen with the release clause. However, it seems that Chelsea have not negotiated further. And long after Napoli reduced the fee, there is still no club that has contacted him to re-negotiate. The final offer was only at £85m and of course this has not yet reached an agreement because it is far below Napoli's initial wishes.
Source: Harry Kane