Your market value is the average of what people with a similar experience and aptitude get.
But while the average may say you are worth say 65k per year, the upper end is more like a million per year, and the lower end near zero.It depends on multiple factors, what industry, what location, what company and how you present during interviews.
At present it is fair to say what you are getting is below average. Doubling your salary shouldn't be difficult if you look around, especially outside Central Europe. It can be difficult since many companies only offer a contract within certain juridictions, but some companies out there are flexible since they want to select from the worldwide pool rather than a fraction of it.
To find your true value. Apply to about 50 jobs you feel you qualify for. A third of it will give you a screening call to show your worth, 5 of them will get you through the final round and probably make you an offer.
Make the average of the offers you get, that's your true value now.
Of course along the way you may hit a great 2nd offer which double your income, you would be tempted to just take it and end the experiment. And you may be right to do so. You can run the experiment again after you switched jobs.
I will throw out there that the best way to get compensated for your true value is to repeat this at least once a year, because too many employers squeeze current employees compensations by not offering the increase they deserve.If you continuously look for jobs you always ensure to have the current information about your current value hence leave no chance to be stuck at some undervalued job.
Of course it's draining to often be on the look out and attend interviews. But it depends how important it is to you.