Need advice on SEO strategy

So, I operate this SaaS, https://convertixo.com, and aim to rank for the keyword “convert website to app.” I’ve been working on this for a year. Initially, I hired an Indian SEO agency, paying $200 each to three different people. Unfortunately, I soon realized they were creating profile links and spam comments.

Subsequently, I opted for Lapaas, an Indian agency associated with a somewhat famous YouTuber. They performed better, creating higher-quality posts and backlinks on superior websites. However, they repeated the same backlinks every month, resulting in a modest improvement in ranking from 100 to around 60. I paid them approximately $1,000.

After that, I decided to handle it myself for the past three months. Since my website is on WordPress, one-page SEO was straightforward. I installed Yoast SEO, followed YouTube videos to create files and add metadata, and hired different freelancers to write blogs regularly. This month, I found a student who writes good blogs with keyword research. For backlinks, I use a broker who creates links on high DA websites (70+), adding one backlink with him each month.

Currently, the ranking is around 65, but the improvement is not significant. I need suggestions—Is my strategy good, or am I doing something wrong? Your help would mean a lot.