To understand this you have to answer one simple question! "What is the language partner going to get out of it?" If you are a native speaker in a language that the partner wishes to learn then you stand more chance. Wanting to find an English language partner who is serious about it is even harder. They have the choice of many, many, offers. I am learning German and I have had many offers to be people's language partner. I specified that what I wanted was a language partner who was a native speaker. This led to a surprising number of contacts which started "I am not a native speaker but..." These were ignored. The answer is probably going to be that you will have to pay for proper lessons. Unfortunately that is life.

Unfortunately there are a lot more people wanting to practise English than wanting to practise Farsi! That is probably the reason why you find it difficult to find someone. There are lots of community tutors on Italki who charge very little for lessons. Or you might find a non-native speaker who also wants to practise their English.

Me too ...