Hello. For the "Silenced Echo" Black Spirit Quest, you must eliminate a monster. Is it absolutely recommended to do the quest in a group ? Is there a little hope of doing it alone ? Even if I farm my character to a certain level ? Fighting in a group is not my strong point, no matter what online game I play (as FF XIV online). Thanks. 

You can do every quest alone in this game. If you have full pen tuvala (probably also tet tuvala is enough), you can easily clear the rift by yourself. It simply takes much longer than with 5 people. But it is definitely possible 

Also worth noting that not using the new slot the echo in the relic method and just right clicking the echo in inventory will give you an easier, more soloable version.

Ok. Thanks. I'll try to put all the chances on my side before starting. If can(t win, then I'll try my luck later.