That means, if i can't lie by omission, i couldn't go to US anymore without this visa???
5 years after you went to Iran you can go to USA either to stay as a tourist or to transit on the Visa Waiver scheme WITHOUT a visa. After 5 years you cn legitimately answer "no" to the question "have you visited xxxxx in the last 5 years?". Before the 5 years are up, the legal requirement is that you apply for visa - which includes a face to face interview. I haven' t yet read a report of anyone who went to Iran for purely "touristic" reasons who has already applied for a visa on these terms ( they are an Obama era thing NOT a Trump one so there ought to be known examples of how the US has acted somewhere on the Web!). One would hope that the US authorities would be sensible.
As for how long a US tourist visa lasts after issue. You can get 10 year visas or 6 mth ones - I don't know the difference in cost or in the likely difference in difficulty of getting one. It partly depends on citizenship ( all other things being equal). If/when you need then do some Web searches!!. Onthis web site both Els and I face this problem having visited Iran last year.
By the way a US visa in UK costs $160 - the French cost may or may not be the same as the German cost.