Can I update 2 columns from 2 tables joined by foreign key with one statement in SAP HANA
No, SAP HANA up to its current version HANA 2 SPS 05 does not support multi-table updates (or inserts/deleted for that matter).
Depending on the use-case, you may be able to emulate the behavior via SQLScript, like e.g. so:
DO BEGIN
data_to_insert = SELECT id, stuff FROM DB;
-- update table 1
UPDATE tab1 t FROM t, :data_to_insert d
SET t.one_stuff = d.stuff
WHERE t.id = d.id;
-- update table 2
UPDATE tab2 t FROM t, :data_to_insert d
SET t.two_stuff = d.stuff
WHERE t.id = d.id;
END;