yes you can use عرف for something you know but mostly the verb علم is used here. e.g.: أنا أعلم أنه كبير I know it/ he is big. I think عرف is more used in Dialects instea of علمbut it is a Fos7a word) فكر: can only be used for "thinking" as I'm thinking about something. for the other meaning you can use ظنّ or اعتقد أظن : I think / I suspect أعتقد: I think/ I believe e.g: أعتقد أنه صادق I think he's honest ( speaking the truth) أظن أنها الحقيقة I think it's the truth أعتقد ذلك أظن كذلك I think so hope I could help :)

yes you can use عرف in i know something is ... like i know something is wrong (أعرف أن شيئا ما خاطئ) == you are sure that something is wrong for فكر you can say i'm thinking (أنا أفكر) but i think so is أظن(أعتقد) هذا so there is no فكر here i think it's true اعتقد(أظن) أن هذا صحيح the verbs اعتقد and اظن means you are not sure of something it's only in your opinion the verb think can means فكر too like in those examples i'm so busy to think about ... انا مشغول جدا لأفكر في

فكر = think فكر = thought عرف = know i think i know you أظن أنيني أعرفك i think about you أنا أفكر فيك i know that person أنا أعرف ذلك الشخص

اعرف وافكر .......اعرف تعنى العلم المؤكد بالامر..... اما عن افكر تعنى الاحتمالية I know and I'm thinking ....... I know means science is certain about it ..... As for the thinking concerned with probability

I meant ظنّ