Port 1337 is already used on VPS

I added inside my .env file:

HOST=0.0.0.0
PORT=1338

and it runs

> my-strapi-project@0.1.0 start /home/srv43578/cms
> strapi start

 Project information
┌────────────────────┬──────────────────────────────────────────────────┐
│ Time               │ Tue Mar 14 2023 19:09:16 GMT+0100 (czas środkow… │
│ Launched in        │ 779 ms                                           │
│ Environment        │ development                                      │
│ Process PID        │ 3216673                                          │
│ Version            │ 4.7.1 (node v14.20.1)                            │
│ Edition            │ Community                                        │
│ Database           │ sqlite                                           │
└────────────────────┴──────────────────────────────────────────────────┘

 Actions available

Welcome back!
To manage your project 🚀, go to the administration panel at:
http://codepage.pl/admin

To access the server ⚡️, go to:
http://codepage.pl

but when I try to enter my /admin page the result is 404 error.

While being inside my page console.log says

GET http://codepage.pl/api/restaurants?fields=name,description&populate=image 503 (Service Unavailable)
Uncaught (in promise) SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

and still the result of command node server.js is:

[cms (14)] [srv43578@h23 cms]$ node server.js
internal/modules/cjs/loader.js:905
  throw err;
  ^

Error: Cannot find module 'strapi'
Require stack:
- /home/srv43578/cms/server.js
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:902:15)
    at Function.Module._load (internal/modules/cjs/loader.js:746:27)
    at Module.require (internal/modules/cjs/loader.js:974:19)
    at require (internal/modules/cjs/helpers.js:101:18)
    at Object.<anonymous> (/home/srv43578/cms/server.js:1:16)
    at Module._compile (internal/modules/cjs/loader.js:1085:14)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)
    at Module.load (internal/modules/cjs/loader.js:950:32)
    at Function.Module._load (internal/modules/cjs/loader.js:790:12)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:75:12) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [ '/home/srv43578/cms/server.js' ]
}