Take it to a tyre shop to mount.. less frustration. The alternative is to look at sourcing the correct tools for the job. Plenty advertised on the internet-net.
I gave up using the 3x tyre lever, rubber hammer, ratchet and finding enough space on the work bench thing. The tyre walls of the modern tyres are too stiff.
In the 1970 /1980's I used to change the tyres myself, but now that I'm older it is easier to pay to have it done. Wiser too, as the rim is checked, the wheel is balanced and down time is minimal.