how to fix this problem about timeline

The first thing to know is that a yellow bar isn't a sign of a problem (nor is a red bar, necessarily).

• green: This segment of the sequence has a rendered preview file associated with it. Playback will play using the rendered preview file. Playback at full quality is certain to be in real time.
• yellow: This segment of the sequence does not have a  rendered preview file associated with it. Playback will play by rendering each frame just before the CTI reaches it. Playback at full quality will probably be in real time (but it might not be).
• red: This segment of the sequence does not have a  rendered preview file associated with it. Playback will play by rendering each frame just before the CTI reaches it. Playback at full quality will probably not be in real time (but it might be).
• none: This segment of the sequence does not have a  rendered preview file associated with it, but the codec of the source media is simple enough that it can essentially be treated as its own preview file. Playback will play directly from the original source media file. Playback at full quality is certain to be in real time. This only occurs for a few codecs (including DV and DVCPRO).

Note the uses of the word probably above. The colors aren’t a  promise. They’re a guess based on some rather simple criteria. If you have a fast computer, then a lot of things marked with red may play back in real time; if you have a slow computer, then some things marked with yellow may need to be rendered to preview files before the segment can be played in real time.

from here:
https://community.adobe.com/t5/premiere-pro-discussions/faq-why-do-i-have-a-red-or-yellow-bar-over-my-sequence-and-how-do-i-render-previews/td-p/3540298

i dont's know why the yellow line just stop there??? i can not  drag the line until to the end ...