". . . I’m sure CCNA can improve my life or at least introduce me to a job."
I believe you're expecting too much from obtaining a CCNA, or pretty much, any certificate.
Usually, certificates (or college degrees) act a a first cut filter to what resumes will be considered or they will be used as a "tie breaker" if all else is equal.
For obtaining a job, work history is important. (Of course, there's the old catch-22 - i.e. employers want to hire experienced employees, but how do you get the experience if they don't hire you?)
Possibly most important is how you do in job interview(s).
Don't misunderstand the above. Obtaining a CCNA is a "good thing"!!! Besides what you'll learn, it demonstrates a commitment to the profession. Again, though, don't think you'll automatically get a job because you have a CCNA.
To your other questions, most of a quality exam's questions shouldn't be tricky, but they do try to determine if you know the subject being tested. If you do, you should be able to pass the test. Regarding English not being your native language, if the test is in English, I can see that will make it more difficult. Not much you can do on that front besides working, also, to improve you proficiency in English or insuring that the test cannot be taken in your native language.
BTW, personally, the first certificate test I ever took was for the ICCP's (then) CDP. (Billed, again then, as the computer industry's version of Accountants CPA.) This test allowed five hours to complete it. (If also had five separate sections, which you passed/failed individually. You needed to pass all five sections to obtain the certificate. You could later, retest, just on failed sections.) It also (at least then) had 2/3s of candidate taking the test fail it.
A book I was using to help study for the test, had sample questions, which I was "lucky" to get 50% correct. No way, at 50%, would I pass the "real" test.
However the actual test was, somewhat easier, so I managed to pass all on the first attempt.
Once I had this difficult to obtain certificate, did jobs doors open left and right? Nope. In fact, to most, what's a "CDP"?
At least Cisco's certificates have a bit more "brand" recognition.
If you wade through my bio, I have three Brocade networking certificates, which probably are comparable to Cisco's CCNA through CCNP levels, not quite to Cisco's CCIE level. At the time, I had read (2009) Network World: Brocade's BCNE most valuable on earth along with being questioned "but you don't have any networking certificates?" Trust me, after obtaining the BCNE, employers didn't start beating down my door with job offers (laugh).
Again, obtaining some like Cisco's CCNA is good(!), but your value, to employers, will come more from understanding what you need to know, to pass the certificate's test, than having the certificate, itself.
