You miss a whitspace on your query, try this one
UPDATE tab SET whoweare = 'text 888', services = '', logo = '', copertina = '', galleria1 = '', galleria2 = '', galleria3 = '', galleria4 = '', indirizzo = 'input 1', tel_fisso = '', tel_mobile = '', orari = 'input 4', social_www = '', social_tw = '', social_fb = '', social_yt = '', social_lin = '' WHERE users_user='try'