I have an SMTP server at a hosting and my domain at another dealer.
I would like to know if it is the supplier of my SMTP server which should provide me with the SPF and DKIM keys or if I generate from my dashboard MailWizz?
Your smtp server provider should give you the dkim/spf records. You could do it from mailwizz as well, but will slow things down better from smtp server side.
Also,
How can I properly configure my sending domains in MailWizz ?
MailWizz generates me automatic SPF and DKIM which are different from those of my SMTP provider.