Galleria Metropolia Theme + Recommended Plugin contact-form-7

So I was applying the new Galleria Metropolia theme in WordPress for a website that I am helping to manage, and then it recommended me to install and activate several plugins. One of them was the contact-form-7, alongside various others such as: cmsmasters-mega-menu, cmsmasters-content-composer, etc.

But then after activating these plugins, I could no longer access either the wp-admin page or the page itself. And the error messages displayed were as follows:

Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 5120 bytes) in /home/oxfordlawsoc/public_html/wp-content/plugins/contact-form-7/modules/recaptcha.php on line 485

(NB: Various line numbers were displayed over the past hour, including 490, 476 and 346)

Hence I would appreciate if anyone on this support forum could kindly let me know what is going on here; I was hoping that the author of the PHP code would probably know what was going on here and be able to help with troubleshooting.