Re: please point out the mistakes in my statements
Don't say "the official website."
If you are writing directly to someone at that company (not an employment office or some other third party) then just say
I'm writing to apply for the software engineer position advertised on your Web site.
Are you sure you want to say you've been at this job for 3 months? That tells me you're a "job hopper" and that you leave jobs quickly. Why should I invest in hiring you and training you if you are going to leave in 3-6 months?
Try "In my current position, I focus on embedded software development."
(I have no idea what that means, but I assume a software developer does.)
Good luck with your job hunt.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.