Hey Mjal... I'll see what I can do to help.
Can you provide a more precise time-frame of when this story was published? (1985, 1990, 2000, 2005, 2010...etc.) Even giving a date within 2 to 5 years of publication would help a great deal. Also, was it published in a newspaper format, or a more modernized comic book format? Was it in color or black & white?
Weekly Comic Mags are mostly known to contain serials (an eclectic collection of stories in an anthology format) and a few popular weeklies came to mind so check out these titles below (I omitted weeklies such as The Dandy, The Beano, The Beezer, Topper, etc. as these consist only humor and not action/adventure.) I don't know which (if any) were translated into other languages, but if any of these titles sound like what you used to read, then that will help narrow down the search for the actual story title itself.
POSSIBLE TITLES: (not a complete list, but it's a start) 2000 AD (IPC Magazines, Fleetway, Rebellion) published 1977 to present Eagle (Hulton Press / IPC Magazines) published 1950 to 1969, then relaunched 1982 to 1994 Action (IPC Magazines) published 1976 to 1977 [short lived and merged with Battle Picture Weekly] Battle Picture Weekly (IPC Magazines) published 1975 to 1988 Valiant (IPC Magazines) published between 1962 to 1976 The Victor (D.C. Thompson Co.) 1,657 issues published from 1961 to 1992 Scream! (IPC Magazines) Weekly British horror comic anthology ran for 15 issues in 1984 Spirou Magazine (Dupuis) published 1938 to present Pilote (Dargaud) [title changed to 'Pilote et Charlie' then back to Piloute] published 1959 to 1989
There are other weekly titles but many ceased publication in the 1970's and 1960's but if that was when you actually had these books (or newspapers, etc.) then I will reply with those other titles as well.
Oddly enough, what you described sounds a lot like a story I read a long time ago about the lost gold of El Dorado which involved conquistadors but I cannot recall what title it was in. Any other additional info will certainly help!
Regards,
*CBK*