I want my Raspberry Pi 4B to create a wireless network that connects to my router, without using any external devices to assist the pi (ie. a secondary router or an antennae that would connect to the pi).
The 4B would connect to a wifi network wirelessly, then I would connect the Pi network. Most tutorials are about the 3 and do not work when I try them. Note that I am a pi beginner, and this is my first project.
OpenWrt is the best choice for you. It makes Raspberry Pi to a wireless router device and you don't need to run a lot of commands. Easy to use with an interactive web user interface named LuCi like picture below:
I believe it going to help you better than in other ways.
The thing you should concern is that you should don't attend this page. As this page, OpenWrt is not on the supported list, however, you can install the bcm2709 by this link - Index of (root) / snapshots / targets / brcm2708 / bcm2709. Download rpi-2-ext4-factory.img.gz and write the image on a larger 256MB SD-Card.
The default IP is 192.168.1.1 and the DHCP server is disabled therefore add and static IP address to the host you want to configure RPi (such as 192.168.1.100), the default user is root and leave the password section blank.
Go to Network/Wireless then turn radio0 or WLAN on.
As I mentioned, it's easy to configure OpenWrt and you can configure it any way you want.
UPDATE:
Raspberry Pi 4 sources provided by the Raspberry Pi Foundation are Linux >= 4.19.
OpenWrt 18.06 is based on Linux 4.9 and OpenWrt 19.07 is based on Linux 4.14, so you need to use the snapshots builds, which are based on Linux 4.19:
https://downloads.openwrt.org/snapshots/targets/brcm2708/bcm2711/
Download rpi-4-ext4-factory.img.gz and write the image to the SD-Card.
UPDATE 02:
Snapshot builds do not include the web interface, the LuCi package. Therefore, follow the procedure:
1. Connect to the Raspberry Pi's terminal via SSH.
2. Update package list of OpenWrt:
opkg update
3. Install LuCi package which is the web interface configuration mode:
opkg install luci
As far as I understand you want to have an access point that is connected with a WiFi client connection as uplink to your internet. All tutorials and automated scripts I know that work with the RasPi are made to use a wired uplink to the internet router router but not a wireless one. This is because it isn't an easy task to have a wireless access point and a wireless client uplink with only the on-board WiFi device. But it is possible if you respect a strict order by managing the network interfaces. How to do it you can look at Access point as WiFi router/repeater, optional with bridge. You only need to install hostapd as helper. All other things are built-in and you only have to configure it.
