Bottleneck finding / hardware recommendations

Nextcloud version (eg, 12.0.2): 16.0.5
Operating system and version (eg, Ubuntu 17.04): Raspbian Buster
Apache or nginx version (eg, Apache 2.4.25): Apache/2.4.38 (Raspbian)
PHP version (eg, 7.1): PHP 7.3.4-2

Ram: 432MiB
CPU: BCM2835 (1) @ 700MHz

Page loading takes multiple minutes per page. I’m fairly certain this is thanks to the Raspberry Pi Model B Rev 2 I’m running the server on. I’m wondering where the bottleneck lies and what the recommended specs are. I’m looking at a banana pi since they have a sata port but apparently they’re just a usb to sata controller. Anyone have any recommendations for hardware?