{Came down} (kat(886c)then).  Mr 1:21  has the historical
present, {they go into} (eisporeuontai). Capernaum (Tell Hum)
is now the headquarters of the Galilean ministry, since Nazareth
has rejected Jesus.  Lu 4:31-37  is parallel with  Mr 1:21-28 
which he manifestly uses. It is the first of Christ's miracles
which they give. {Was teaching them} ((886e) didask(936e) autous).
Periphrastic imperfect. Mark has edidasken first and then en
didask(936e). "Them" here means the people present in the synagogue
on the sabbath, construction according to sense as in  Mr 1:22 .