Amateur Dramatic society website re-write into WordPress

I built a very simple website on a web builder software, but it is not open source and so cannot be moved.
I want to get a much nicer looking WordPress website with exactly the same content.
https://winterslowdrama.co.uk/ is the current website. This is a village group and is not-for-profit so cost is absolutely critical
It must be on WordPress. Would like all content copied as it is but on a much nicer-looking site, and with all images able to be changed very simply. Must avoid massively bloated WordPress with lots of plugins which always cause vulnerabilities. I would need to know what plugins may have to be bought.
Most past performances have a gallery. Ideally I would want to be able to load full-size images and WordPress compresses them to small file size for performance.
Ticket sales are done on ECWID, so I would supply code to get that integrated.
Main changes are adding new performances to Future Productions, then moving these to "Past Productions" after the performance, when galleries are then added.
The same URLs and all SEO are essential. I can supply a screaming frog extract of it all.