Hi Mattia, sorry for the delay in responding further. You could try to output to a file in your VOSpace "vos://myfile.csv". Depending on the table size (both nrows and ncols), but also on what else is going on on the servers, this might work better.
Finally, some found that writing the results of a query to a file straight in your notebook directory is fastest. For instance, this:
q = "select * from gaia_edr3.gaia_source limit 1000000"
res = qc.query(sql=q,out='./myfile_gaia_1e6.csv')
takes about 2m40s and writes out a file of almost 1GB to your NB directory. From there, you can e.g. download it through the browser (right-click, Download).
Hope this is somewhat helpful.