Translation:On Thursday I was writing about my experiences.
i would argue that "doświadczenia" are more "research results" than experiences
Wouldn't it mean that you have been doing it until now or you have just finished it?
so if it is not finished at all and i might be going on writing sometimes later could i say then i have been writing?
Polish distinguishes in the past and future between imperfective and perfective verbs. Perfective verbs carry the meaning of doing something completely/finishing it. Imperfective verbs (like "pisać" here) accent the fact of lasting of the action and say nothing about the effect. I could finish it without completing the action, I could do it also for some time since then. I could complete this action as well. It is not stated explicitly. Neither from English nor from Polish sentence it follows directly that I didn't finish the action or I have been doing it till now and the action is currently in progress. What we know for sure is the fact that "On Thursday I was writing about my experiences" (and nothing more). If I wanted to say that "I have been writing about my experiences since Thursday (and I am still doing it)", I would say: "Piszę o moich doświadczeniach od czwartku".
You can read more about perfective and imperfective verbs for example here: https://www.duolingo.com/comment/12975268
Have been doing it does not mean it is not finished. You could finish right now and say "I have been writing about my experiences all week until now".
Should "experience" also be accepted to account for the uncountable case? For example, if one wrote about their work experience, this translation would need the uncountable form of the word. http://ell.stackexchange.com/questions/34843/is-experience-countable-or-uncountable
Just as drzwi might mean door and not doors, I believe doświadczenia can mean experience as well (though for different reasons). On a resume, for example, you say experience. This form of experience is uncountable. In fact, in my dialect experience is almost always treated as uncountable, though I guess it is used as a countable word in some cases elsewhere.
Another example of an uncountable noun is sand. "The sand is hot." "There is a lot of sand."
On a CV it will be uncountable "doświadczenie".
If you come back from a six months long trip around India, you will tell your friends about your "doświadczenia".
. what were you wanting to do with the CV
wherein lies with the doswiadczenie/a