Speaking in front of a large audience is always difficult. You have already imagined how clearly, interestingly and consistently you express your thoughts, how people applaud you and your brilliant ideas. What is really going on? You are nervous, afraid, and all your theses disappear somewhere. But everything is not so scary. The ability to present your thoughts is based on a few simple and logical truths.

First, you need to compose your speech. For this:

•                analyze what you want to say to your audience and formulate your idea;
•                use simple and understandable language so that you can easily imagine what you are talking about;
•                do not be afraid to give examples, tell real cases or even joke - people love to laugh;
•                at the end of the presentation, do not forget to draw conclusions and repeat the main idea again.

Second, you need to develop visual aids for your presentation:

•                one slide should describe only one idea;
•                use pictures for your presentation - it helps the audience to better imagine what you are talking about;
•                if you use tables, make them as accessible and clear as possible;
•                the font should be large so that even from the back rows the slides are easy to read;
•                keep track of the timing of your presentation.

Third, prepare yourself well:

•                You should know your speech well and understand the material - you should not sight-read, it is better to speak by establishing eye contact with the audience.

The following phrases will help you prepare to speak in English:

Start of presentation, introductory sentences:   

•                Let me begin by explaining ...
•                First / Now I want (would like) to talk about ...
•                Let's (now) find out why / how ...
•                Let's now move to ...
•                As I already indicated, stated, mentioned ...
•                Another aspect / point is that ...
•                As you probably (perhaps) know, ...
•                At the beginning ...
•                It is claimed (stated, indicated) that ...
•                For instance , for example ...    
•                One can say that ...

Comments on pictures, slides

•                Let me use a graphic to explain this.
•                The graphic shows that ...
•                As you can see (in the picture) ...
•                In the next / following picture, you can see ...
•                Here is another picture .
•                The next picture shows how ...
•                I think the picture perfectly shows how / that ...

Conclusion, repetition of the main idea

•                In conclusion …,
•                As a result ...,
•                To summarize ...,
•                That brings me to the end of the presentation.
•                It was a great success for ...
•                This proves that ...
•                The reason is that ...
•                The result of this is that ...
•                In other words , ...
•                I want to repeat that ...
•                I'd (just) like to add ...

You can also find help tp make your English speeches better here: https://essayassistant.org/english-homework-help/ as well as watch some famous speeches of great people.  

Be sure to leave 5-10 minutes for questions at the end of your talk.