嘿嘿，又见到你啦！
1 请走在马路内侧
Please walk on the inside lane of the road
Please walk in the inside lane of the road
我比较喜欢第二句
2 请靠马路右侧 走路 / 骑车 （自行车）
Please walk on the right side of the road
Please bike on the right side of the road (bike 做动词)
或
Please ride your bike on the right side of the road
3 不要长时间走在马路中间
Do not stay or walk in the middle of the road for too long
我觉得 for too long 在这句子里是冗余的，可以省略.
4 请把自行车扶起来
Please pick the bike up.
5 请把刚才滑到的老人扶起来
Please help up the elderly gentleman who just fell.
Please help the elderly gentleman,who just tripped,get up.
第一句比较简洁.
