Should I find a job just for 2 months

Not that I advocate it but I think you'd need to lie. 99.99% of employers won't have much interest in someone wanting to work for about 8 weekends and nothing else, in terms of training they'd barely get any use out of you before you left, esp since you'd be starting from 0 exp.

just want to know will they usually keep my job if I will be back after 4 months

Nah no chance tbh
If you're hiring for entry level part time work you want people ready to start with little to no fuss, 8 weekends then away for 4 months isn't any use to anyone and would likely upset a lot of the other staff.
Think about it, if they're advertising a job needing done, why would they be willing to wait 4 months for you with the work not getting done when they could just hire someone who is available? In interviews you often get asked if you have any holidays etc booked and they normally honour them, but as soon as you say '4 months' they will pretty much end the interview and move on to next name on their list.