Very slow opening everything

I recently deleted several things from my Samsung phone. They were things/Apps? that were already installed or that I installed and no longer needed. However, since doing this my phone has been excruciatingly slow to open everything from emails, photo's, texts, WhatsApp etc. In fact absolutely everything. I can't even remember what I deleted. I mistakingly and naively thought that deleting them would make my battery last longer. Now when I try to open anything I just get a blank black or white screen for ages before it opens. How can I remedy this please.
Many thanks in advance......J

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