Hi Elena, welcome to the forum!
You have a lovely and rare Tissot chronograph in stainless steel and based on a Lemania 15CHT movement, circa 1937. Dials came in both black and white (like yours) with big bold numerals at the 12 and 6. As you mention, your watch has some damaged parts and is missing the subdial hands and at least one gear/wheel. Finding spare parts will be very difficult although I have occasionally seen scrapped watches and Lemania movement parts come up for sale. You will need a lot of patience and a skilled watchmaker to bring your watch back to life. On a positive note, the hour and minutes hands are correct for this watch as is the desirable steel case and dial.
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