Using regular expressions for working with HTML data is not recommended, consider using CSS Selector Extractor
Add CSS Selector Extractor as a child of the previous sampler which returns the login page
Configure it as follows:
Name of created variable: anything meaningful, i.e. token
CSS Selector Expression: input[name=_csrf]
In next ...
As per Let's Start chapter of JMeter Getting Started Guide
If you want to perform JDBC testing, then you will, of course, need the appropriate JDBC driver from your vendor. JMeter does not come with any JDBC drivers.
So make sure to download Oracle JDBC Driver and drop it to JMeter Classpath.
And don't forget to restart JMeter to pick the .jar up.
JMeter treats the system as a "black box", if you think that one request is consuming more resources than others you can try to run the requests separately.
If for some reason you cannot split the test to run API request independently you can consider using a profiler tool on server side in order to check which request is to blame.
Additionally you can ...
Your scenario is not compatible with the JMeter's thread model, you cannot slow down only one request in the Thread Group without slowing down the rest.
You could consider moving the 5th request to another Thread Group and configure the desired requests rate by adding a Constant Timer or a Constant Throughput Timer.
In order to pass the token between 1st ...
You cannot concatenate JMeter Variables this way, in order to evaluate nested JMeter Variables you need to use __V() function like:
More information: Here’s What to Do to Combine Multiple JMeter Variables