How long does it take to become an anesthesiologist? That is my dream career but I want to know what can be the most difficult part of that job.

Not an easy one. You will need to complete medical school (4 years) and then be accepted in residency. This is another 4 years, at least. Plus you may add years that you will spend doing your undergraduate education (another 4 years) getting all the credits necessary before entering medical school.
12+ Years After HS. In most cases, anesthesiologists have at least 12 years of schooling/training after high school (4 years of undergrad, 4 years of medical school, and 4 years of residency training). Many continue onwards to pursue 1 year fellowships in fields like pediatrics, regional anesthesia, pain, etc.
12 years. It is an exceptional career, filled with challenges both in terms of diagnostics and therapeutics. After high school, you'll need to complete a 4 year bachelor's program, followed by a 4 year medical school degree (md or do), a 1 year internship, then the 3 year anesthesiology residency. There are 1 year post residency fellowships as well, but those are not required to practice anesthesia.
12 to 13 years. University degree (bsc or ba) - 4 years medical school - 4 years internship and residency - 4 years then possibly fellowship after that. (1 year) most difficult part of job is probably the brief time you get to spend with a patient before their anesthetic. You only have a short time in which to build a rapport with the patient, before they are sedated for the operating room.
Years. 4 yr undergrad+ 4 yr med school+4 yr residency+ 1-2 yr sub specialty if desired = 12 to 14 years training . 8 of the 12 to 14 years need to be paid for by you and the last 4 to 6 years a minimum wage to help pay for your cost of living. For the average person you can expect years of hard work and great debt so you have to really want it.
12 - 13 years. Four years of college, four years of medical school, one year of internship, three years of residency and then one year of fellowship if you want to specialize. The most difficult part of the job for me is losing. That is having a patient die during surgery. One thing anesthesiologists are really good at is keeping patients alive.
12 years. To become an anesthesiologist in the United States, one must complete high school, attain a bachelor's degree from a university, fulfill pre-medical prerequisite classes, take the mcat exam, attend a four year medical school, complete a four year residency program, and pass the american board of anesthesiology written and oral exams.
Many years &worth it. Anesthesiologists are physicians who complete 4 (or more) years of additional training after medical school. The most "difficult" part of the job is probably different for each person. It requires a detail oriented personality and an eagerness to ensure a patient's comfort and safety, and analyze and treat any medical issue that comes up during surgery. See if you can volunteer in an anesth dept.
4 years. An anesthesiology residency is 4 years long with potentially additional training for subspecialization in areas like critical care and cardiac anesthesia. This is in addition to the 4-6 years spent in medical school.