visa (artist) extension, lawyer or self procedure? Haven’t been a year so no pension and tax data.

I got my artist visa granted and moved in this Feb,19
And was told that I can be able to apply to extend the visa 3 months before expire, so I’m ready to submit it now.

I wonder if I need to find a lawyer to do this or do it myself, so I’m here to look for someone that has self application experience.

My first ever application was done by 行政書士, and he told me that I can apply it on my own for the second time, (or either I can pay for the help)

I got in Japan on 19 Feb, until now, so I don’t have any tax, pension data ( actually they couldn’t find it because it hasn’t even been one year since I got in)
So the immigration office near me told me that I can just write a reason letter ( and gave me a reason letter form) and submit it.
(Does someone have this kind of experience?)

I got my first salary in May, and my company does pay my pension and tax so I’m not quite worry about this, but yet, I’m still nervous about the result, if I failed, I’ll need to sell all my furniture I purchased and I don’t want to be back to my country sooooo bad(Taiwan)

So kinda just come up here to ask for some advice to ease my anxiety lol

Hopefully I can get a 3 years visa this time.