Few simple commands to update Your Magento 2.2.x to latest 2.3.x:
composer require magento/product-community-edition 2.3.4 --no-update
composer update
rm -rf var/cache/* var/page_cache/* generated/code/*
# ensure maintenance is on before running setup:upgrade as this may result in failed upgrade when crons are accessing files
php bin/magento setup:upgrade
n98-magerun2 cache:flush
Upgrading to a security patch update
clearmage2 --safe-dist-upgrade