GW2 generally does not support Addons/Mods as you might know them from WoW or ESO. There are a few that are kinda tolerated (see Sidebar/Addons).

As for lack of direction, the game heavily rewards exploration, i. e. almost eveything you do (even gathering materials) grants experience and leads to your character leveling up and getting more abilities.

So my suggestion is to go to zones with a level range (shown on the world map) around your character's level and it explore them, i. e. unlock Waypoints, visit POIs and Vistas, do Renown Hearts and last but not least engage in Events popping up near you.

Every 10 levels you are prompted (by in-game mail) to progress your Personal Story which will take you to zones you may or may not have explored yet.

There's not addons like fx in World of Warcraft. You can take a look at the sidebar and check out the addons available for Guild Wars 2. It's not a lot :))

Maybe changing the size of your UI can help you?

There are addons but these are considered being rather a QoL features. Theres dps meter and bunch of overlays providing information while playing the game, and also an addon which helps you change mounts more easily. Game itself allows to hide some UI elements and call them upon mouse hover. But theres nothing that would mod the interface itself.

Heres the policy regarding addons: https://help.guildwars2.com/hc/en-us/articles/360013625034-Policy-Third-Party-Programs

The solution would be to take your time and get used to the UI - GW2 does lots of things differently

UI mods are not a thing, no. The best you can get is some overlays that put additional stuff on the screen.