Domain Being too Young and Can't Get Ranking Improved Further?

Hello guys.
Our website is in the machinery and packaging automation niche, while the domain age is only 1yr 40 days only...

I believe that we have been blogging with excellent content and during last year when we had not built strong links we've already had some mediocre ranking around 4th or 5th page with some kws.
Two pages even once stroke to 4th and 5th ranking in google UK during a period (though disappeared afterwards...)
I believe the content is fine.

Since the April, I have been both guest-positing on my own, and then passed to purchase PBN links.
Now I found with some primary keywords we are stuck at the 2nd page, fluctuating there and can not move further to touch even the bottom of 1st page...


Some competitors there in the 1st page are basically some well-know global companies with 10yr+ or 20yr+ domain age.
But there are also few local Chinese companies whose pages are just full of plagiarized images and shitty bad-writen content, yet domain age basically beyond 6yr.

I am just wondering, maybe we are too young to strike higher ranking.
The problems, when we get 2yr domain age, that of a competitor also get 1 year older... The gap is always there...

What am I supposed to do with our ranking?

first don't do pbn

Like you are saying you have excellent content, then keep doing that. And do some internal linking because that helps too much.

And how many guest posts and PBNs you have built?

Since your competitors are big fish then 4-5 guest posts are gonna do nothing.

I don't think domain age matters at all after 7-8 months. Try working on getting more authoritative backlinks, and keep writing more content covering the same topic