The U.S. Citizenship and Immigration Services (USCIS), an agency of the U.S. Department of Homeland Security (DHS), administers the nation's naturalization and immigration system. The USCIS website provides information on how to obtain U.S. citizenship. The USCIS website also provides information on the Uniting for Ukraine program (information on the program is available also in Ukrainian and Russian), which is not a citizenship program; more information on the Uniting for Ukraine program is given at the DHS Website.
The USCIS provides many resources at the Citizenship Resource Center, and you should work through these carefully if you are interested in becoming a citizen. The process involves two tests, the English test and the civics test. Your ability to speak and understand English is assessed by: (i) a USCIS officer during your eligibility interview; and (ii) your ability to correctly read aloud one out of three sentences. The USCIS has published a four-part video series about this. Study materials for the (2008 version) of the civics test involves learning the answers to a predefined set of 100 questions; updates to the test are given in this page. The USCIS publishes PDF flashcards, a pocket study guide, a 20-question practice test, and many other items here (to see the entire list of available items, you may need to click on the Next > label at the bottom of that page).
Candidates who are 65 years or older and who have lived in the U.S. as lawful permanent residents for 20 years or more need only study the 20 questions marked with asterisks in the list of 100 questions. There are other exceptions and accommodations as well.
You should not consider the selection of resources that we have provided links to above as authoritative, exhaustive, or complete, but should yourself refer to the primary source, the USCIS website for definitive information.
You may find this audio resource for the 128-question 2020 version of the civics test helpful. (Note that you are unlikely to have to take the 2020 version as it is the 2008 version that is again the currently-used one.) This video pertains to the 2008 version of the civics test; please note, however, that it is not produced by the US government or any of its agencies.