Beginner bombed with errors

1. Where in the settings do I disable suggestions about modification accessibility of a script? I have certain variables where I didn't mention access type i.e. "public", "private" to which I think "Why don't you just shut up?", it's meant to be the way it is. That's one it can be shut about. After looking up, I was told to disable "Enable solution wide analysis" setting, but it seems to disable almost everything. I don't want to miss out on 80% of all Rider has to over, just to remove green annoying underline from my scripts.

2. JetBrains Rider 2019.2.3 doesn't recognize System. It does recognize namespaces of Unity and two other custom namespaces, but does not recognize normal things like "bool", "int", "void", it does recognize "true", "false" and ".0001f" and words like "public". How do I get it to work? Even custom namespace's class are ignored in autocomplete and even when explicitly typed out.

Tried following:

- https://rider-support.jetbrains.com/hc/en-us/community/posts/360000372779/comments/360000081259 (either didn't apply or fix didn't work)

- https://github.com/JetBrains/resharper-unity/issues/799 (already has those as default settings)

3. Inconsistent modifiers style? What decides what type of style is consistent in context of modifiers? What is the primary axiom?

4. "Namespace does not correspond to file location". People on StackOverflow tell me to move my script to a provided directory, but what if I don't want to? Is there a way to silence it too?

5. "Return value is missing", I would be stunned if "void" had to return a value.

All of these errors give me impression that one particular thing is missing, a setting, URL, dependency, something... something is responsible for all of this.

And after we could get those fixed, there are probably more coming...

MSBuild: Auto detected (16.0)
Whatever this is:
JetBrains Rider 2019.2.3
Build #RD-192.7317.11, built on October 16, 2019
Licensed to Rider Evaluator
Expiration date: December 23, 2019
Runtime version: 11.0.4+10-b304.77 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 10 10.0
GC: ParNew, ConcurrentMarkSweep
Memory: 1450M
Cores: 6
Registry: ide.tree.horizontal.default.autoscrolling=false, performance.watcher.sampling.interval.ms=200, ide.borderless.title.product=false, performance.watcher.unresponsive.interval.ms=1000, ide.tooltip.initialDelay.highlighter=0, search.everywhere.settings=true, parameter.info.max.visible.rows=10, ide.win.file.chooser.native=true, ide.borderless.title.project.path=false, search.everywhere.pattern.checking=false, ide.tooltip.initialDelay=0, ide.borderless.title.classpath=false, ide.require.transaction.for.model.changes=false
Non-Bundled Plugins:

I'm sorry if I posted to wrong forum, I think "Community" is least incorrect.
Also, switching from Visual Studio, that's a terrible first impression.