Thank you for all your replies. I will answer some questions, in this message.

"What do you find weird in this relationship?" The weird part is, that if I didn't know she has a boyfriend I would be like 99% sure she is interested.

"Why would you pursue someone who’s not available?" Connections like these are rare, it's like a magnetic attraction. I would be angry with myself for the rest of my life if I didn't try to maintain contact with her more. And it's still more on her side to say no, if she is the one in relationship.

"you claim you are fine to only be friends with her" I am, but those mixed signals are giving me feeling that I may be something more than a friend and I am fine with that too.

"why are you asking her for meetings and pursuing her" I actually wanted to ask her out even before I knew she has a boyfriend, but I was not 100% sure she is single so I asked her what was she doing during the vacation, expecting that she will mention a boyfriend if she has one and she did. After this some weeks passed and we were still in contact, so I decided to ask her out anyway as I was eager to speak with her again and couldn't help myself (I was actually angry with myself, that I am pathetic and my bestfriend told me that I am crazy, but I did it anyway as there was basically not any other option to me) and she surprisingly (to me) agreed. The second meeting was proposed by her. The third one by me and when we were saying goodbye to eachother she said that we will hopefully see each other again soon. Also in our WA conversation I am not sending her some random messages, I am mostly answering her questions and I am asking questions much less than her. The longest period when we didn't exchange any message (only one week) was ended by her. So I would not say that I am pursuing her very much, I just keeping the relationship going same like her.

"There are plenty single unattached women you can go for" Connections like these are pretty rare, I would say that most people will connect with somebody like this just a couple times in their lives, many people will not experience that in their whole life. And I not mean it only in romantic way, also friendships like these are rare. Basically all of my friendships developed trough a much longer time, in which we were basically forced to be together (like in school, work, hobbies or hangin out with mutual friends). This friendship started just after a few meetings and there was just only one week since then when we didn't exchange atleast one message. I even told her that it's so weird that we didn't even talk when we were working together and now we are like best friends and she agreed.

"Either just continue friendship and professional relationship or just stop it all together" I am doing that, I am not planning to do any romantic gesture till she is not single or till I know she is not happy in her current relationship.

I wrote on this forum because I am interested in whether people have experienced a similar relationship in their lives, because to me it's completely new and thus weird. If you think that I am a bad guy for keeping this relationship going you might be right, but I bet that you would act very similar if you were in my situation.